diff --git a/awss3-storage/src/main/java/com/netflix/conductor/s3/storage/S3PayloadStorage.java b/awss3-storage/src/main/java/com/netflix/conductor/s3/storage/S3PayloadStorage.java
index 86e57e685d..8ac530ea54 100644
--- a/awss3-storage/src/main/java/com/netflix/conductor/s3/storage/S3PayloadStorage.java
+++ b/awss3-storage/src/main/java/com/netflix/conductor/s3/storage/S3PayloadStorage.java
@@ -22,7 +22,8 @@
 
 import com.netflix.conductor.common.run.ExternalStorageLocation;
 import com.netflix.conductor.common.utils.ExternalPayloadStorage;
-import com.netflix.conductor.core.exception.ApplicationException;
+import com.netflix.conductor.core.exception.NonTransientException;
+import com.netflix.conductor.core.exception.TransientException;
 import com.netflix.conductor.core.utils.IDGenerator;
 import com.netflix.conductor.s3.config.S3Properties;
 
@@ -104,11 +105,11 @@ public ExternalStorageLocation getLocation(
                             "Error communicating with S3 - operation:%s, payloadType: %s, path: %s",
                             operation, payloadType, path);
             LOGGER.error(msg, e);
-            throw new ApplicationException(ApplicationException.Code.BACKEND_ERROR, msg, e);
+            throw new TransientException(msg, e);
         } catch (URISyntaxException e) {
             String msg = "Invalid URI Syntax";
             LOGGER.error(msg, e);
-            throw new ApplicationException(ApplicationException.Code.INTERNAL_ERROR, msg, e);
+            throw new NonTransientException(msg, e);
         }
     }
 
@@ -135,7 +136,7 @@ public void upload(String path, InputStream payload, long payloadSize) {
                     String.format(
                             "Error uploading to S3 - path:%s, payloadSize: %d", path, payloadSize);
             LOGGER.error(msg, e);
-            throw new ApplicationException(ApplicationException.Code.BACKEND_ERROR, msg, e);
+            throw new TransientException(msg, e);
         }
     }
 
@@ -154,7 +155,7 @@ public InputStream download(String path) {
         } catch (SdkClientException e) {
             String msg = String.format("Error downloading from S3 - path:%s", path);
             LOGGER.error(msg, e);
-            throw new ApplicationException(ApplicationException.Code.BACKEND_ERROR, msg, e);
+            throw new TransientException(msg, e);
         }
     }
 
diff --git a/cassandra-persistence/src/main/java/com/netflix/conductor/cassandra/dao/CassandraBaseDAO.java b/cassandra-persistence/src/main/java/com/netflix/conductor/cassandra/dao/CassandraBaseDAO.java
index c576be8e91..b327c18fbb 100644
--- a/cassandra-persistence/src/main/java/com/netflix/conductor/cassandra/dao/CassandraBaseDAO.java
+++ b/cassandra-persistence/src/main/java/com/netflix/conductor/cassandra/dao/CassandraBaseDAO.java
@@ -13,11 +13,13 @@
 package com.netflix.conductor.cassandra.dao;
 
 import java.io.IOException;
+import java.util.UUID;
 
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 import com.netflix.conductor.cassandra.config.CassandraProperties;
+import com.netflix.conductor.core.exception.NonTransientException;
 import com.netflix.conductor.metrics.Monitors;
 
 import com.datastax.driver.core.DataType;
@@ -110,6 +112,14 @@ public CassandraBaseDAO(
         init();
     }
 
+    protected static UUID toUUID(String uuidString, String message) {
+        try {
+            return UUID.fromString(uuidString);
+        } catch (IllegalArgumentException iae) {
+            throw new IllegalArgumentException(message + " " + uuidString, iae);
+        }
+    }
+
     private void init() {
         try {
             if (!initialized) {
@@ -226,7 +236,7 @@ String toJson(Object value) {
         try {
             return objectMapper.writeValueAsString(value);
         } catch (JsonProcessingException e) {
-            throw new RuntimeException(e);
+            throw new NonTransientException("Error serializing to json", e);
         }
     }
 
@@ -234,7 +244,7 @@ <T> T readValue(String json, Class<T> clazz) {
         try {
             return objectMapper.readValue(json, clazz);
         } catch (IOException e) {
-            throw new RuntimeException(e);
+            throw new NonTransientException("Error de-serializing json", e);
         }
     }
 
diff --git a/cassandra-persistence/src/main/java/com/netflix/conductor/cassandra/dao/CassandraEventHandlerDAO.java b/cassandra-persistence/src/main/java/com/netflix/conductor/cassandra/dao/CassandraEventHandlerDAO.java
index ce797cea9e..4ce0126046 100644
--- a/cassandra-persistence/src/main/java/com/netflix/conductor/cassandra/dao/CassandraEventHandlerDAO.java
+++ b/cassandra-persistence/src/main/java/com/netflix/conductor/cassandra/dao/CassandraEventHandlerDAO.java
@@ -28,8 +28,7 @@
 import com.netflix.conductor.cassandra.config.CassandraProperties;
 import com.netflix.conductor.cassandra.util.Statements;
 import com.netflix.conductor.common.metadata.events.EventHandler;
-import com.netflix.conductor.core.exception.ApplicationException;
-import com.netflix.conductor.core.exception.ApplicationException.Code;
+import com.netflix.conductor.core.exception.TransientException;
 import com.netflix.conductor.dao.EventHandlerDAO;
 import com.netflix.conductor.metrics.Monitors;
 
@@ -37,6 +36,7 @@
 import com.datastax.driver.core.ResultSet;
 import com.datastax.driver.core.Row;
 import com.datastax.driver.core.Session;
+import com.datastax.driver.core.exceptions.DriverException;
 import com.fasterxml.jackson.databind.ObjectMapper;
 
 import static com.netflix.conductor.cassandra.util.Constants.EVENT_HANDLER_KEY;
@@ -96,7 +96,7 @@ public void removeEventHandler(String name) {
             Monitors.error(CLASS_NAME, "removeEventHandler");
             String errorMsg = String.format("Failed to remove event handler: %s", name);
             LOGGER.error(errorMsg, e);
-            throw new ApplicationException(Code.BACKEND_ERROR, errorMsg, e);
+            throw new TransientException(errorMsg, e);
         }
         refreshEventHandlersCache();
     }
@@ -154,11 +154,11 @@ private List<EventHandler> getAllEventHandlersFromDB() {
                     .map(row -> readValue(row.getString(EVENT_HANDLER_KEY), EventHandler.class))
                     .collect(Collectors.toList());
 
-        } catch (Exception e) {
+        } catch (DriverException e) {
             Monitors.error(CLASS_NAME, "getAllEventHandlersFromDB");
             String errorMsg = "Failed to get all event handlers";
             LOGGER.error(errorMsg, e);
-            throw new ApplicationException(Code.BACKEND_ERROR, errorMsg, e);
+            throw new TransientException(errorMsg, e);
         }
     }
 
@@ -168,14 +168,14 @@ private void insertOrUpdateEventHandler(EventHandler eventHandler) {
             session.execute(insertEventHandlerStatement.bind(eventHandler.getName(), handler));
             recordCassandraDaoRequests("storeEventHandler");
             recordCassandraDaoPayloadSize("storeEventHandler", handler.length(), "n/a", "n/a");
-        } catch (Exception e) {
+        } catch (DriverException e) {
             Monitors.error(CLASS_NAME, "insertOrUpdateEventHandler");
             String errorMsg =
                     String.format(
                             "Error creating/updating event handler: %s/%s",
                             eventHandler.getName(), eventHandler.getEvent());
             LOGGER.error(errorMsg, e);
-            throw new ApplicationException(Code.BACKEND_ERROR, errorMsg, e);
+            throw new TransientException(errorMsg, e);
         }
         refreshEventHandlersCache();
     }
diff --git a/cassandra-persistence/src/main/java/com/netflix/conductor/cassandra/dao/CassandraExecutionDAO.java b/cassandra-persistence/src/main/java/com/netflix/conductor/cassandra/dao/CassandraExecutionDAO.java
index f8184f4b56..ea0c12aef2 100644
--- a/cassandra-persistence/src/main/java/com/netflix/conductor/cassandra/dao/CassandraExecutionDAO.java
+++ b/cassandra-persistence/src/main/java/com/netflix/conductor/cassandra/dao/CassandraExecutionDAO.java
@@ -23,8 +23,9 @@
 import com.netflix.conductor.cassandra.util.Statements;
 import com.netflix.conductor.common.metadata.events.EventExecution;
 import com.netflix.conductor.common.metadata.tasks.TaskDef;
-import com.netflix.conductor.core.exception.ApplicationException;
-import com.netflix.conductor.core.exception.ApplicationException.Code;
+import com.netflix.conductor.core.exception.NonTransientException;
+import com.netflix.conductor.core.exception.NotFoundException;
+import com.netflix.conductor.core.exception.TransientException;
 import com.netflix.conductor.dao.ConcurrentExecutionLimitDAO;
 import com.netflix.conductor.dao.ExecutionDAO;
 import com.netflix.conductor.metrics.Monitors;
@@ -32,6 +33,7 @@
 import com.netflix.conductor.model.WorkflowModel;
 
 import com.datastax.driver.core.*;
+import com.datastax.driver.core.exceptions.DriverException;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.base.Preconditions;
@@ -181,6 +183,7 @@ public List<TaskModel> getTasks(String taskType, String startKey, int count) {
     public List<TaskModel> createTasks(List<TaskModel> tasks) {
         validateTasks(tasks);
         String workflowId = tasks.get(0).getWorkflowInstanceId();
+        UUID workflowUUID = toUUID(workflowId, "Invalid workflow id");
         try {
             WorkflowMetadata workflowMetadata = getWorkflowMetadata(workflowId);
             int totalTasks = workflowMetadata.getTotalTasks() + tasks.size();
@@ -192,8 +195,7 @@ public List<TaskModel> createTasks(List<TaskModel> tasks) {
                         task.setScheduledTime(System.currentTimeMillis());
                         session.execute(
                                 updateTaskLookupStatement.bind(
-                                        UUID.fromString(workflowId),
-                                        UUID.fromString(task.getTaskId())));
+                                        workflowUUID, toUUID(task.getTaskId(), "Invalid task id")));
                     });
 
             // update all the tasks in the workflow using batch
@@ -203,7 +205,7 @@ public List<TaskModel> createTasks(List<TaskModel> tasks) {
                         String taskPayload = toJson(task);
                         batchStatement.add(
                                 insertTaskStatement.bind(
-                                        UUID.fromString(workflowId),
+                                        workflowUUID,
                                         DEFAULT_SHARD_ID,
                                         task.getTaskId(),
                                         taskPayload));
@@ -216,25 +218,22 @@ public List<TaskModel> createTasks(List<TaskModel> tasks) {
                                 task.getWorkflowType());
                     });
             batchStatement.add(
-                    updateTotalTasksStatement.bind(
-                            totalTasks, UUID.fromString(workflowId), DEFAULT_SHARD_ID));
+                    updateTotalTasksStatement.bind(totalTasks, workflowUUID, DEFAULT_SHARD_ID));
             session.execute(batchStatement);
 
             // update the total tasks and partitions for the workflow
             session.execute(
                     updateTotalPartitionsStatement.bind(
-                            DEFAULT_TOTAL_PARTITIONS, totalTasks, UUID.fromString(workflowId)));
+                            DEFAULT_TOTAL_PARTITIONS, totalTasks, workflowUUID));
 
             return tasks;
-        } catch (ApplicationException e) {
-            throw e;
-        } catch (Exception e) {
+        } catch (DriverException e) {
             Monitors.error(CLASS_NAME, "createTasks");
             String errorMsg =
                     String.format(
                             "Error creating %d tasks for workflow: %s", tasks.size(), workflowId);
             LOGGER.error(errorMsg, e);
-            throw new ApplicationException(Code.BACKEND_ERROR, errorMsg, e);
+            throw new TransientException(errorMsg, e);
         }
     }
 
@@ -260,14 +259,14 @@ public void updateTask(TaskModel task) {
                     addTaskToLimit(task);
                 }
             }
-        } catch (Exception e) {
+        } catch (DriverException e) {
             Monitors.error(CLASS_NAME, "updateTask");
             String errorMsg =
                     String.format(
                             "Error updating task: %s in workflow: %s",
                             task.getTaskId(), task.getWorkflowInstanceId());
             LOGGER.error(errorMsg, e);
-            throw new ApplicationException(Code.BACKEND_ERROR, errorMsg, e);
+            throw new TransientException(errorMsg, e);
         }
     }
 
@@ -308,14 +307,14 @@ public boolean exceedsLimit(TaskModel task) {
                 Monitors.recordTaskConcurrentExecutionLimited(task.getTaskDefName(), limit);
                 return true;
             }
-        } catch (Exception e) {
+        } catch (DriverException e) {
             Monitors.error(CLASS_NAME, "exceedsLimit");
             String errorMsg =
                     String.format(
                             "Failed to get in progress limit - %s:%s in workflow :%s",
                             task.getTaskDefName(), task.getTaskId(), task.getWorkflowInstanceId());
             LOGGER.error(errorMsg, e);
-            throw new ApplicationException(Code.BACKEND_ERROR, errorMsg);
+            throw new TransientException(errorMsg);
         }
         return false;
     }
@@ -358,13 +357,11 @@ public TaskModel getTask(String taskId) {
                                 return task;
                             })
                     .orElse(null);
-        } catch (ApplicationException ae) {
-            throw ae;
-        } catch (Exception e) {
+        } catch (DriverException e) {
             Monitors.error(CLASS_NAME, "getTask");
             String errorMsg = String.format("Error getting task by id: %s", taskId);
             LOGGER.error(errorMsg, e);
-            throw new ApplicationException(Code.BACKEND_ERROR, errorMsg);
+            throw new TransientException(errorMsg);
         }
     }
 
@@ -412,12 +409,12 @@ public String createWorkflow(WorkflowModel workflow) {
 
             workflow.setTasks(tasks);
             return workflow.getWorkflowId();
-        } catch (Exception e) {
+        } catch (DriverException e) {
             Monitors.error(CLASS_NAME, "createWorkflow");
             String errorMsg =
                     String.format("Error creating workflow: %s", workflow.getWorkflowId());
             LOGGER.error(errorMsg, e);
-            throw new ApplicationException(Code.BACKEND_ERROR, errorMsg, e);
+            throw new TransientException(errorMsg, e);
         }
     }
 
@@ -435,12 +432,12 @@ public String updateWorkflow(WorkflowModel workflow) {
                             payload, UUID.fromString(workflow.getWorkflowId())));
             workflow.setTasks(tasks);
             return workflow.getWorkflowId();
-        } catch (Exception e) {
+        } catch (DriverException e) {
             Monitors.error(CLASS_NAME, "updateWorkflow");
             String errorMsg =
                     String.format("Failed to update workflow: %s", workflow.getWorkflowId());
             LOGGER.error(errorMsg, e);
-            throw new ApplicationException(Code.BACKEND_ERROR, errorMsg);
+            throw new TransientException(errorMsg);
         }
     }
 
@@ -457,11 +454,11 @@ public boolean removeWorkflow(String workflowId) {
                                 deleteWorkflowStatement.bind(
                                         UUID.fromString(workflowId), DEFAULT_SHARD_ID));
                 removed = resultSet.wasApplied();
-            } catch (Exception e) {
+            } catch (DriverException e) {
                 Monitors.error(CLASS_NAME, "removeWorkflow");
                 String errorMsg = String.format("Failed to remove workflow: %s", workflowId);
                 LOGGER.error(errorMsg, e);
-                throw new ApplicationException(Code.BACKEND_ERROR, errorMsg);
+                throw new TransientException(errorMsg);
             }
             workflow.getTasks().forEach(this::removeTaskLookup);
         }
@@ -495,14 +492,15 @@ public WorkflowModel getWorkflow(String workflowId) {
 
     @Override
     public WorkflowModel getWorkflow(String workflowId, boolean includeTasks) {
-        WorkflowModel workflow = null;
+        UUID workflowUUID = toUUID(workflowId, "Invalid workflow id");
         try {
+            WorkflowModel workflow = null;
             ResultSet resultSet;
             if (includeTasks) {
                 resultSet =
                         session.execute(
                                 selectWorkflowWithTasksStatement.bind(
-                                        UUID.fromString(workflowId), DEFAULT_SHARD_ID));
+                                        workflowUUID, DEFAULT_SHARD_ID));
                 List<TaskModel> tasks = new ArrayList<>();
 
                 List<Row> rows = resultSet.all();
@@ -518,8 +516,7 @@ public WorkflowModel getWorkflow(String workflowId, boolean includeTasks) {
                         TaskModel task = readValue(row.getString(PAYLOAD_KEY), TaskModel.class);
                         tasks.add(task);
                     } else {
-                        throw new ApplicationException(
-                                ApplicationException.Code.INTERNAL_ERROR,
+                        throw new NonTransientException(
                                 String.format(
                                         "Invalid row with entityKey: %s found in datastore for workflow: %s",
                                         entityKey, workflowId));
@@ -532,8 +529,7 @@ public WorkflowModel getWorkflow(String workflowId, boolean includeTasks) {
                     workflow.setTasks(tasks);
                 }
             } else {
-                resultSet =
-                        session.execute(selectWorkflowStatement.bind(UUID.fromString(workflowId)));
+                resultSet = session.execute(selectWorkflowStatement.bind(workflowUUID));
                 workflow =
                         Optional.ofNullable(resultSet.one())
                                 .map(
@@ -549,18 +545,11 @@ public WorkflowModel getWorkflow(String workflowId, boolean includeTasks) {
                                 .orElse(null);
             }
             return workflow;
-        } catch (ApplicationException e) {
-            throw e;
-        } catch (IllegalArgumentException e) {
-            Monitors.error(CLASS_NAME, "getWorkflow");
-            String errorMsg = String.format("Invalid workflow id: %s", workflowId);
-            LOGGER.error(errorMsg, e);
-            throw new ApplicationException(Code.INVALID_INPUT, errorMsg, e);
-        } catch (Exception e) {
+        } catch (DriverException e) {
             Monitors.error(CLASS_NAME, "getWorkflow");
             String errorMsg = String.format("Failed to get workflow: %s", workflowId);
             LOGGER.error(errorMsg, e);
-            throw new ApplicationException(Code.BACKEND_ERROR, errorMsg);
+            throw new TransientException(errorMsg);
         }
     }
 
@@ -645,14 +634,14 @@ public boolean addEventExecution(EventExecution eventExecution) {
                                     eventExecution.getId(),
                                     jsonPayload))
                     .wasApplied();
-        } catch (Exception e) {
+        } catch (DriverException e) {
             Monitors.error(CLASS_NAME, "addEventExecution");
             String errorMsg =
                     String.format(
                             "Failed to add event execution for event: %s, handler: %s",
                             eventExecution.getEvent(), eventExecution.getName());
             LOGGER.error(errorMsg, e);
-            throw new ApplicationException(Code.BACKEND_ERROR, errorMsg);
+            throw new TransientException(errorMsg);
         }
     }
 
@@ -670,14 +659,14 @@ public void updateEventExecution(EventExecution eventExecution) {
                             eventExecution.getMessageId(),
                             eventExecution.getName(),
                             eventExecution.getId()));
-        } catch (Exception e) {
+        } catch (DriverException e) {
             Monitors.error(CLASS_NAME, "updateEventExecution");
             String errorMsg =
                     String.format(
                             "Failed to update event execution for event: %s, handler: %s",
                             eventExecution.getEvent(), eventExecution.getName());
             LOGGER.error(errorMsg, e);
-            throw new ApplicationException(Code.BACKEND_ERROR, errorMsg);
+            throw new TransientException(errorMsg);
         }
     }
 
@@ -690,14 +679,14 @@ public void removeEventExecution(EventExecution eventExecution) {
                             eventExecution.getMessageId(),
                             eventExecution.getName(),
                             eventExecution.getId()));
-        } catch (Exception e) {
+        } catch (DriverException e) {
             Monitors.error(CLASS_NAME, "removeEventExecution");
             String errorMsg =
                     String.format(
                             "Failed to remove event execution for event: %s, handler: %s",
                             eventExecution.getEvent(), eventExecution.getName());
             LOGGER.error(errorMsg, e);
-            throw new ApplicationException(Code.BACKEND_ERROR, errorMsg);
+            throw new TransientException(errorMsg);
         }
     }
 
@@ -712,13 +701,13 @@ List<EventExecution> getEventExecutions(
                     .filter(row -> !row.isNull(PAYLOAD_KEY))
                     .map(row -> readValue(row.getString(PAYLOAD_KEY), EventExecution.class))
                     .collect(Collectors.toList());
-        } catch (Exception e) {
+        } catch (DriverException e) {
             String errorMsg =
                     String.format(
                             "Failed to fetch event executions for event: %s, handler: %s",
                             eventName, eventHandlerName);
             LOGGER.error(errorMsg, e);
-            throw new ApplicationException(Code.BACKEND_ERROR, errorMsg);
+            throw new TransientException(errorMsg);
         }
     }
 
@@ -732,14 +721,14 @@ public void addTaskToLimit(TaskModel task) {
                             UUID.fromString(task.getWorkflowInstanceId()),
                             task.getTaskDefName(),
                             UUID.fromString(task.getTaskId())));
-        } catch (Exception e) {
+        } catch (DriverException e) {
             Monitors.error(CLASS_NAME, "addTaskToLimit");
             String errorMsg =
                     String.format(
                             "Error updating taskDefLimit for task - %s:%s in workflow: %s",
                             task.getTaskDefName(), task.getTaskId(), task.getWorkflowInstanceId());
             LOGGER.error(errorMsg, e);
-            throw new ApplicationException(Code.BACKEND_ERROR, errorMsg, e);
+            throw new TransientException(errorMsg, e);
         }
     }
 
@@ -751,14 +740,14 @@ public void removeTaskFromLimit(TaskModel task) {
             session.execute(
                     deleteTaskDefLimitStatement.bind(
                             task.getTaskDefName(), UUID.fromString(task.getTaskId())));
-        } catch (Exception e) {
+        } catch (DriverException e) {
             Monitors.error(CLASS_NAME, "removeTaskFromLimit");
             String errorMsg =
                     String.format(
                             "Error updating taskDefLimit for task - %s:%s in workflow: %s",
                             task.getTaskDefName(), task.getTaskId(), task.getWorkflowInstanceId());
             LOGGER.error(errorMsg, e);
-            throw new ApplicationException(Code.BACKEND_ERROR, errorMsg, e);
+            throw new TransientException(errorMsg, e);
         }
     }
 
@@ -791,11 +780,11 @@ private boolean removeTask(TaskModel task) {
                 removeTaskFromLimit(task);
             }
             return resultSet.wasApplied();
-        } catch (Exception e) {
+        } catch (DriverException e) {
             Monitors.error(CLASS_NAME, "removeTask");
             String errorMsg = String.format("Failed to remove task: %s", task.getTaskId());
             LOGGER.error(errorMsg, e);
-            throw new ApplicationException(Code.BACKEND_ERROR, errorMsg);
+            throw new TransientException(errorMsg);
         }
     }
 
@@ -808,13 +797,11 @@ private void removeTaskLookup(TaskModel task) {
                 removeTaskFromLimit(task);
             }
             session.execute(deleteTaskLookupStatement.bind(UUID.fromString(task.getTaskId())));
-        } catch (ApplicationException ae) {
-            // no-op
-        } catch (Exception e) {
+        } catch (DriverException e) {
             Monitors.error(CLASS_NAME, "removeTaskLookup");
             String errorMsg = String.format("Failed to remove task lookup: %s", task.getTaskId());
             LOGGER.error(errorMsg, e);
-            throw new ApplicationException(Code.BACKEND_ERROR, errorMsg);
+            throw new TransientException(errorMsg);
         }
     }
 
@@ -838,8 +825,7 @@ void validateTasks(List<TaskModel> tasks) {
                         .filter(task -> !workflowId.equals(task.getWorkflowInstanceId()))
                         .findAny();
         if (optionalTask.isPresent()) {
-            throw new ApplicationException(
-                    Code.INTERNAL_ERROR,
+            throw new NonTransientException(
                     "Tasks of multiple workflows cannot be created/updated simultaneously");
         }
     }
@@ -859,31 +845,24 @@ WorkflowMetadata getWorkflowMetadata(String workflowId) {
                         })
                 .orElseThrow(
                         () ->
-                                new ApplicationException(
-                                        Code.NOT_FOUND,
-                                        String.format(
-                                                "Workflow with id: %s not found in data store",
-                                                workflowId)));
+                                new NotFoundException(
+                                        "Workflow with id: %s not found in data store",
+                                        workflowId));
     }
 
     @VisibleForTesting
     String lookupWorkflowIdFromTaskId(String taskId) {
+        UUID taskUUID = toUUID(taskId, "Invalid task id");
         try {
-            ResultSet resultSet =
-                    session.execute(selectTaskLookupStatement.bind(UUID.fromString(taskId)));
+            ResultSet resultSet = session.execute(selectTaskLookupStatement.bind(taskUUID));
             return Optional.ofNullable(resultSet.one())
                     .map(row -> row.getUUID(WORKFLOW_ID_KEY).toString())
                     .orElse(null);
-        } catch (IllegalArgumentException iae) {
-            Monitors.error(CLASS_NAME, "lookupWorkflowIdFromTaskId");
-            String errorMsg = String.format("Invalid task id: %s", taskId);
-            LOGGER.error(errorMsg, iae);
-            throw new ApplicationException(Code.INVALID_INPUT, errorMsg, iae);
-        } catch (Exception e) {
+        } catch (DriverException e) {
             Monitors.error(CLASS_NAME, "lookupWorkflowIdFromTaskId");
             String errorMsg = String.format("Failed to lookup workflowId from taskId: %s", taskId);
             LOGGER.error(errorMsg, e);
-            throw new ApplicationException(Code.BACKEND_ERROR, errorMsg, e);
+            throw new TransientException(errorMsg, e);
         }
     }
 }
diff --git a/cassandra-persistence/src/main/java/com/netflix/conductor/cassandra/dao/CassandraMetadataDAO.java b/cassandra-persistence/src/main/java/com/netflix/conductor/cassandra/dao/CassandraMetadataDAO.java
index 0187034b51..21fe61741b 100644
--- a/cassandra-persistence/src/main/java/com/netflix/conductor/cassandra/dao/CassandraMetadataDAO.java
+++ b/cassandra-persistence/src/main/java/com/netflix/conductor/cassandra/dao/CassandraMetadataDAO.java
@@ -34,8 +34,8 @@
 import com.netflix.conductor.cassandra.util.Statements;
 import com.netflix.conductor.common.metadata.tasks.TaskDef;
 import com.netflix.conductor.common.metadata.workflow.WorkflowDef;
-import com.netflix.conductor.core.exception.ApplicationException;
-import com.netflix.conductor.core.exception.ApplicationException.Code;
+import com.netflix.conductor.core.exception.ConflictException;
+import com.netflix.conductor.core.exception.TransientException;
 import com.netflix.conductor.dao.MetadataDAO;
 import com.netflix.conductor.metrics.Monitors;
 
@@ -43,6 +43,7 @@
 import com.datastax.driver.core.ResultSet;
 import com.datastax.driver.core.Row;
 import com.datastax.driver.core.Session;
+import com.datastax.driver.core.exceptions.DriverException;
 import com.fasterxml.jackson.databind.ObjectMapper;
 
 import static com.netflix.conductor.cassandra.util.Constants.TASK_DEFINITION_KEY;
@@ -157,11 +158,11 @@ public void removeTaskDef(String name) {
         try {
             recordCassandraDaoRequests("removeTaskDef");
             session.execute(deleteTaskDefStatement.bind(name));
-        } catch (Exception e) {
+        } catch (DriverException e) {
             Monitors.error(CLASS_NAME, "removeTaskDef");
             String errorMsg = String.format("Failed to remove task definition: %s", name);
             LOGGER.error(errorMsg, e);
-            throw new ApplicationException(Code.BACKEND_ERROR, errorMsg, e);
+            throw new TransientException(errorMsg, e);
         }
         refreshTaskDefsCache();
     }
@@ -176,11 +177,9 @@ public void createWorkflowDef(WorkflowDef workflowDef) {
                                     workflowDef.getVersion(),
                                     workflowDefinition))
                     .wasApplied()) {
-                throw new ApplicationException(
-                        Code.CONFLICT,
-                        String.format(
-                                "Workflow: %s, version: %s already exists!",
-                                workflowDef.getName(), workflowDef.getVersion()));
+                throw new ConflictException(
+                        "Workflow: %s, version: %s already exists!",
+                        workflowDef.getName(), workflowDef.getVersion());
             }
             String workflowDefIndex =
                     getWorkflowDefIndexValue(workflowDef.getName(), workflowDef.getVersion());
@@ -190,16 +189,14 @@ public void createWorkflowDef(WorkflowDef workflowDef) {
             recordCassandraDaoRequests("createWorkflowDef");
             recordCassandraDaoPayloadSize(
                     "createWorkflowDef", workflowDefinition.length(), "n/a", workflowDef.getName());
-        } catch (ApplicationException ae) {
-            throw ae;
-        } catch (Exception e) {
+        } catch (DriverException e) {
             Monitors.error(CLASS_NAME, "createWorkflowDef");
             String errorMsg =
                     String.format(
                             "Error creating workflow definition: %s/%d",
                             workflowDef.getName(), workflowDef.getVersion());
             LOGGER.error(errorMsg, e);
-            throw new ApplicationException(ApplicationException.Code.BACKEND_ERROR, errorMsg, e);
+            throw new TransientException(errorMsg, e);
         }
     }
 
@@ -218,14 +215,14 @@ public void updateWorkflowDef(WorkflowDef workflowDef) {
             recordCassandraDaoRequests("updateWorkflowDef");
             recordCassandraDaoPayloadSize(
                     "updateWorkflowDef", workflowDefinition.length(), "n/a", workflowDef.getName());
-        } catch (Exception e) {
+        } catch (DriverException e) {
             Monitors.error(CLASS_NAME, "updateWorkflowDef");
             String errorMsg =
                     String.format(
                             "Error updating workflow definition: %s/%d",
                             workflowDef.getName(), workflowDef.getVersion());
             LOGGER.error(errorMsg, e);
-            throw new ApplicationException(ApplicationException.Code.BACKEND_ERROR, errorMsg, e);
+            throw new TransientException(errorMsg, e);
         }
     }
 
@@ -253,11 +250,11 @@ public Optional<WorkflowDef> getWorkflowDef(String name, int version) {
                                                     WorkflowDef.class))
                             .orElse(null);
             return Optional.ofNullable(workflowDef);
-        } catch (Exception e) {
+        } catch (DriverException e) {
             Monitors.error(CLASS_NAME, "getTaskDef");
             String errorMsg = String.format("Error fetching workflow def: %s/%d", name, version);
             LOGGER.error(errorMsg, e);
-            throw new ApplicationException(Code.BACKEND_ERROR, errorMsg, e);
+            throw new TransientException(errorMsg, e);
         }
     }
 
@@ -268,12 +265,12 @@ public void removeWorkflowDef(String name, Integer version) {
             session.execute(
                     deleteWorkflowDefIndexStatement.bind(
                             WORKFLOW_DEF_INDEX_KEY, getWorkflowDefIndexValue(name, version)));
-        } catch (Exception e) {
+        } catch (DriverException e) {
             Monitors.error(CLASS_NAME, "removeWorkflowDef");
             String errorMsg =
                     String.format("Failed to remove workflow definition: %s/%d", name, version);
             LOGGER.error(errorMsg, e);
-            throw new ApplicationException(Code.BACKEND_ERROR, errorMsg, e);
+            throw new TransientException(errorMsg, e);
         }
     }
 
@@ -299,11 +296,11 @@ public List<WorkflowDef> getAllWorkflowDefs() {
                             })
                     .filter(Objects::nonNull)
                     .collect(Collectors.toList());
-        } catch (Exception e) {
+        } catch (DriverException e) {
             Monitors.error(CLASS_NAME, "getAllWorkflowDefs");
             String errorMsg = "Error retrieving all workflow defs";
             LOGGER.error(errorMsg, e);
-            throw new ApplicationException(Code.BACKEND_ERROR, errorMsg, e);
+            throw new TransientException(errorMsg, e);
         }
     }
 
@@ -330,11 +327,11 @@ private TaskDef getTaskDefFromDB(String name) {
             return Optional.ofNullable(resultSet.one())
                     .map(row -> readValue(row.getString(TASK_DEFINITION_KEY), TaskDef.class))
                     .orElse(null);
-        } catch (Exception e) {
+        } catch (DriverException e) {
             Monitors.error(CLASS_NAME, "getTaskDef");
             String errorMsg = String.format("Failed to get task def: %s", name);
             LOGGER.error(errorMsg, e);
-            throw new ApplicationException(Code.BACKEND_ERROR, errorMsg, e);
+            throw new TransientException(errorMsg, e);
         }
     }
 
@@ -350,11 +347,11 @@ private List<TaskDef> getAllTaskDefsFromDB() {
             return rows.stream()
                     .map(row -> readValue(row.getString(TASK_DEFINITION_KEY), TaskDef.class))
                     .collect(Collectors.toList());
-        } catch (Exception e) {
+        } catch (DriverException e) {
             Monitors.error(CLASS_NAME, "getAllTaskDefs");
             String errorMsg = "Failed to get all task defs";
             LOGGER.error(errorMsg, e);
-            throw new ApplicationException(Code.BACKEND_ERROR, errorMsg, e);
+            throw new TransientException(errorMsg, e);
         }
     }
 
@@ -375,11 +372,11 @@ private List<WorkflowDef> getAllWorkflowDefVersions(String name) {
                                             row.getString(WORKFLOW_DEFINITION_KEY),
                                             WorkflowDef.class))
                     .collect(Collectors.toList());
-        } catch (Exception e) {
+        } catch (DriverException e) {
             Monitors.error(CLASS_NAME, "getAllWorkflowDefVersions");
             String errorMsg = String.format("Failed to get workflows defs for : %s", name);
             LOGGER.error(errorMsg, e);
-            throw new ApplicationException(Code.BACKEND_ERROR, errorMsg, e);
+            throw new TransientException(errorMsg, e);
         }
     }
 
@@ -390,12 +387,12 @@ private String insertOrUpdateTaskDef(TaskDef taskDef) {
             recordCassandraDaoRequests("storeTaskDef");
             recordCassandraDaoPayloadSize(
                     "storeTaskDef", taskDefinition.length(), taskDef.getName(), "n/a");
-        } catch (Exception e) {
+        } catch (DriverException e) {
             Monitors.error(CLASS_NAME, "insertOrUpdateTaskDef");
             String errorMsg =
                     String.format("Error creating/updating task definition: %s", taskDef.getName());
             LOGGER.error(errorMsg, e);
-            throw new ApplicationException(Code.BACKEND_ERROR, errorMsg, e);
+            throw new TransientException(errorMsg, e);
         }
         refreshTaskDefsCache();
         return taskDef.getName();
diff --git a/cassandra-persistence/src/test/groovy/com/netflix/conductor/cassandra/dao/CassandraExecutionDAOSpec.groovy b/cassandra-persistence/src/test/groovy/com/netflix/conductor/cassandra/dao/CassandraExecutionDAOSpec.groovy
index 8500d9552e..7afd273afb 100644
--- a/cassandra-persistence/src/test/groovy/com/netflix/conductor/cassandra/dao/CassandraExecutionDAOSpec.groovy
+++ b/cassandra-persistence/src/test/groovy/com/netflix/conductor/cassandra/dao/CassandraExecutionDAOSpec.groovy
@@ -16,7 +16,7 @@ import com.netflix.conductor.common.metadata.events.EventExecution
 import com.netflix.conductor.common.metadata.tasks.TaskDef
 import com.netflix.conductor.common.metadata.workflow.WorkflowDef
 import com.netflix.conductor.common.metadata.workflow.WorkflowTask
-import com.netflix.conductor.core.exception.ApplicationException
+import com.netflix.conductor.core.exception.NonTransientException
 import com.netflix.conductor.core.utils.IDGenerator
 import com.netflix.conductor.model.TaskModel
 import com.netflix.conductor.model.WorkflowModel
@@ -25,7 +25,6 @@ import spock.lang.Subject
 
 import static com.netflix.conductor.common.metadata.events.EventExecution.Status.COMPLETED
 import static com.netflix.conductor.common.metadata.events.EventExecution.Status.IN_PROGRESS
-import static com.netflix.conductor.core.exception.ApplicationException.Code.INVALID_INPUT
 
 class CassandraExecutionDAOSpec extends CassandraSpec {
 
@@ -60,7 +59,7 @@ class CassandraExecutionDAOSpec extends CassandraSpec {
         executionDAO.validateTasks(tasks)
 
         then:
-        def ex = thrown(ApplicationException.class)
+        def ex = thrown(NonTransientException.class)
         ex.message == "Tasks of multiple workflows cannot be created/updated simultaneously"
     }
 
@@ -339,15 +338,13 @@ class CassandraExecutionDAOSpec extends CassandraSpec {
         executionDAO.getTask('invalid_id')
 
         then:
-        def ex = thrown(ApplicationException.class)
-        ex && ex.code == INVALID_INPUT
+        thrown(IllegalArgumentException.class)
 
         when: 'verify that a non-conforming uuid throws an exception'
         executionDAO.getWorkflow('invalid_id', true)
 
         then:
-        ex = thrown(ApplicationException.class)
-        ex && ex.code == INVALID_INPUT
+        thrown(IllegalArgumentException.class)
 
         and: 'verify that a non-existing generated id returns null'
         executionDAO.getTask(new IDGenerator().generate()) == null
diff --git a/core/src/main/java/com/netflix/conductor/core/config/ConductorCoreConfiguration.java b/core/src/main/java/com/netflix/conductor/core/config/ConductorCoreConfiguration.java
index eedef68f1a..9b443377e0 100644
--- a/core/src/main/java/com/netflix/conductor/core/config/ConductorCoreConfiguration.java
+++ b/core/src/main/java/com/netflix/conductor/core/config/ConductorCoreConfiguration.java
@@ -14,7 +14,6 @@
 
 import java.util.List;
 import java.util.Map;
-import java.util.Optional;
 import java.util.Set;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
@@ -29,14 +28,12 @@
 import org.springframework.boot.context.properties.EnableConfigurationProperties;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
-import org.springframework.retry.RetryContext;
-import org.springframework.retry.backoff.NoBackOffPolicy;
-import org.springframework.retry.policy.SimpleRetryPolicy;
 import org.springframework.retry.support.RetryTemplate;
 
 import com.netflix.conductor.common.metadata.tasks.TaskType;
 import com.netflix.conductor.common.utils.ExternalPayloadStorage;
 import com.netflix.conductor.core.events.EventQueueProvider;
+import com.netflix.conductor.core.exception.TransientException;
 import com.netflix.conductor.core.execution.mapper.TaskMapper;
 import com.netflix.conductor.core.execution.tasks.WorkflowSystemTask;
 import com.netflix.conductor.core.listener.WorkflowStatusListener;
@@ -47,7 +44,6 @@
 
 import static com.netflix.conductor.core.events.EventQueues.EVENT_QUEUE_PROVIDERS_QUALIFIER;
 import static com.netflix.conductor.core.execution.tasks.SystemTaskRegistry.ASYNC_SYSTEM_TASKS_QUALIFIER;
-import static com.netflix.conductor.core.utils.Utils.isTransientException;
 
 import static java.util.function.Function.identity;
 
@@ -120,24 +116,10 @@ public Map<String, EventQueueProvider> getEventQueueProviders(
 
     @Bean
     public RetryTemplate onTransientErrorRetryTemplate() {
-        SimpleRetryPolicy retryPolicy = new CustomRetryPolicy();
-        retryPolicy.setMaxAttempts(3);
-
-        RetryTemplate retryTemplate = new RetryTemplate();
-        retryTemplate.setRetryPolicy(retryPolicy);
-        retryTemplate.setBackOffPolicy(new NoBackOffPolicy());
-        return retryTemplate;
-    }
-
-    public static class CustomRetryPolicy extends SimpleRetryPolicy {
-
-        @Override
-        public boolean canRetry(final RetryContext context) {
-            final Optional<Throwable> lastThrowable =
-                    Optional.ofNullable(context.getLastThrowable());
-            return lastThrowable
-                    .map(throwable -> super.canRetry(context) && isTransientException(throwable))
-                    .orElseGet(() -> super.canRetry(context));
-        }
+        return RetryTemplate.builder()
+                .retryOn(TransientException.class)
+                .maxAttempts(3)
+                .noBackoff()
+                .build();
     }
 }
diff --git a/core/src/main/java/com/netflix/conductor/core/dal/ExecutionDAOFacade.java b/core/src/main/java/com/netflix/conductor/core/dal/ExecutionDAOFacade.java
index d23c4f5a25..a295fed517 100644
--- a/core/src/main/java/com/netflix/conductor/core/dal/ExecutionDAOFacade.java
+++ b/core/src/main/java/com/netflix/conductor/core/dal/ExecutionDAOFacade.java
@@ -40,9 +40,9 @@
 import com.netflix.conductor.common.utils.ExternalPayloadStorage;
 import com.netflix.conductor.core.config.ConductorProperties;
 import com.netflix.conductor.core.events.queue.Message;
-import com.netflix.conductor.core.exception.ApplicationException;
-import com.netflix.conductor.core.exception.ApplicationException.Code;
+import com.netflix.conductor.core.exception.NotFoundException;
 import com.netflix.conductor.core.exception.TerminateWorkflowException;
+import com.netflix.conductor.core.exception.TransientException;
 import com.netflix.conductor.core.utils.ExternalPayloadStorageUtils;
 import com.netflix.conductor.dao.*;
 import com.netflix.conductor.metrics.Monitors;
@@ -146,11 +146,8 @@ public WorkflowModel getWorkflowModel(String workflowId, boolean includeTasks) {
      * @param workflowId the id of the workflow to be fetched
      * @param includeTasks if true, fetches the {@link Task} data in the workflow.
      * @return the {@link Workflow} object
-     * @throws ApplicationException if
-     *     <ul>
-     *       <li>no such {@link Workflow} is found
-     *       <li>parsing the {@link Workflow} object fails
-     *     </ul>
+     * @throws NotFoundException no such {@link Workflow} is found.
+     * @throws TransientException parsing the {@link Workflow} object fails.
      */
     public Workflow getWorkflow(String workflowId, boolean includeTasks) {
         return getWorkflowModelFromDataStore(workflowId, includeTasks).toWorkflow();
@@ -164,7 +161,7 @@ private WorkflowModel getWorkflowModelFromDataStore(String workflowId, boolean i
             if (json == null) {
                 String errorMsg = String.format("No such workflow found by id: %s", workflowId);
                 LOGGER.error(errorMsg);
-                throw new ApplicationException(ApplicationException.Code.NOT_FOUND, errorMsg);
+                throw new NotFoundException(errorMsg);
             }
 
             try {
@@ -175,8 +172,7 @@ private WorkflowModel getWorkflowModelFromDataStore(String workflowId, boolean i
             } catch (IOException e) {
                 String errorMsg = String.format("Error reading workflow: %s", workflowId);
                 LOGGER.error(errorMsg);
-                throw new ApplicationException(
-                        ApplicationException.Code.BACKEND_ERROR, errorMsg, e);
+                throw new TransientException(errorMsg, e);
             }
         }
         return workflow;
@@ -204,7 +200,7 @@ public List<Workflow> getWorkflowsByCorrelationId(
                             workflowId -> {
                                 try {
                                     return getWorkflow(workflowId, includeTasks);
-                                } catch (ApplicationException e) {
+                                } catch (NotFoundException e) {
                                     // This might happen when the workflow archival failed and the
                                     // workflow was removed from primary datastore
                                     LOGGER.error(
@@ -340,25 +336,16 @@ public void removeFromPendingWorkflow(String workflowType, String workflowId) {
      *     removal from {@link ExecutionDAO}
      */
     public void removeWorkflow(String workflowId, boolean archiveWorkflow) {
-        try {
-            WorkflowModel workflow = getWorkflowModelFromDataStore(workflowId, true);
+        WorkflowModel workflow = getWorkflowModelFromDataStore(workflowId, true);
 
+        try {
             removeWorkflowIndex(workflow, archiveWorkflow);
-            // remove workflow from DAO
-            try {
-                executionDAO.removeWorkflow(workflowId);
-            } catch (Exception ex) {
-                Monitors.recordDaoError("executionDao", "removeWorkflow");
-                throw ex;
-            }
-        } catch (ApplicationException ae) {
-            throw ae;
-        } catch (Exception e) {
-            throw new ApplicationException(
-                    ApplicationException.Code.BACKEND_ERROR,
-                    "Error removing workflow: " + workflowId,
-                    e);
+        } catch (JsonProcessingException e) {
+            throw new TransientException("Workflow can not be serialized to json", e);
         }
+
+        executionDAO.removeWorkflow(workflowId);
+
         try {
             queueDAO.remove(DECIDER_QUEUE, workflowId);
         } catch (Exception e) {
@@ -377,8 +364,7 @@ private void removeWorkflowIndex(WorkflowModel workflow, boolean archiveWorkflow
                         new String[] {RAW_JSON_FIELD, ARCHIVED_FIELD},
                         new Object[] {objectMapper.writeValueAsString(workflow), true});
             } else {
-                throw new ApplicationException(
-                        Code.INVALID_INPUT,
+                throw new IllegalArgumentException(
                         String.format(
                                 "Cannot archive workflow: %s with status: %s",
                                 workflow.getWorkflowId(), workflow.getStatus()));
@@ -389,29 +375,6 @@ private void removeWorkflowIndex(WorkflowModel workflow, boolean archiveWorkflow
         }
     }
 
-    public void removeWorkflowWithExpiry(
-            String workflowId, boolean archiveWorkflow, int ttlSeconds) {
-        try {
-            WorkflowModel workflow = getWorkflowModelFromDataStore(workflowId, true);
-
-            removeWorkflowIndex(workflow, archiveWorkflow);
-            // remove workflow from DAO with TTL
-            try {
-                executionDAO.removeWorkflowWithExpiry(workflowId, ttlSeconds);
-            } catch (Exception ex) {
-                Monitors.recordDaoError("executionDao", "removeWorkflow");
-                throw ex;
-            }
-        } catch (ApplicationException ae) {
-            throw ae;
-        } catch (Exception e) {
-            throw new ApplicationException(
-                    ApplicationException.Code.BACKEND_ERROR,
-                    "Error removing workflow: " + workflowId,
-                    e);
-        }
-    }
-
     /**
      * Reset the workflow state by removing from the {@link ExecutionDAO} and removing this workflow
      * from the {@link IndexDAO}.
@@ -419,21 +382,16 @@ public void removeWorkflowWithExpiry(
      * @param workflowId the workflow id to be reset
      */
     public void resetWorkflow(String workflowId) {
+        getWorkflowModelFromDataStore(workflowId, true);
+        executionDAO.removeWorkflow(workflowId);
         try {
-            getWorkflowModelFromDataStore(workflowId, true);
-            executionDAO.removeWorkflow(workflowId);
             if (properties.isAsyncIndexingEnabled()) {
                 indexDAO.asyncRemoveWorkflow(workflowId);
             } else {
                 indexDAO.removeWorkflow(workflowId);
             }
-        } catch (ApplicationException ae) {
-            throw ae;
         } catch (Exception e) {
-            throw new ApplicationException(
-                    ApplicationException.Code.BACKEND_ERROR,
-                    "Error resetting workflow state: " + workflowId,
-                    e);
+            throw new TransientException("Error resetting workflow state: " + workflowId, e);
         }
     }
 
@@ -490,21 +448,23 @@ public long getInProgressTaskCount(String taskDefName) {
      * stores it in the {@link IndexDAO}.
      *
      * @param taskModel the task to be updated in the data store
-     * @throws ApplicationException if the dao operations fail
+     * @throws TransientException if the {@link IndexDAO} or {@link ExecutionDAO} operations fail.
+     * @throws com.netflix.conductor.core.exception.NonTransientException if the externalization of
+     *     payload fails.
      */
     public void updateTask(TaskModel taskModel) {
-        try {
-            if (taskModel.getStatus() != null) {
-                if (!taskModel.getStatus().isTerminal()
-                        || (taskModel.getStatus().isTerminal() && taskModel.getUpdateTime() == 0)) {
-                    taskModel.setUpdateTime(System.currentTimeMillis());
-                }
-                if (taskModel.getStatus().isTerminal() && taskModel.getEndTime() == 0) {
-                    taskModel.setEndTime(System.currentTimeMillis());
-                }
+        if (taskModel.getStatus() != null) {
+            if (!taskModel.getStatus().isTerminal()
+                    || (taskModel.getStatus().isTerminal() && taskModel.getUpdateTime() == 0)) {
+                taskModel.setUpdateTime(System.currentTimeMillis());
             }
-            externalizeTaskData(taskModel);
-            executionDAO.updateTask(taskModel);
+            if (taskModel.getStatus().isTerminal() && taskModel.getEndTime() == 0) {
+                taskModel.setEndTime(System.currentTimeMillis());
+            }
+        }
+        externalizeTaskData(taskModel);
+        executionDAO.updateTask(taskModel);
+        try {
             /*
              * Indexing a task for every update adds a lot of volume. That is ok but if async indexing
              * is enabled and tasks are stored in memory until a block has completed, we would lose a lot
@@ -523,7 +483,7 @@ public void updateTask(TaskModel taskModel) {
                             "Error updating task: %s in workflow: %s",
                             taskModel.getTaskId(), taskModel.getWorkflowInstanceId());
             LOGGER.error(errorMsg, e);
-            throw new ApplicationException(ApplicationException.Code.BACKEND_ERROR, errorMsg, e);
+            throw new TransientException(errorMsg, e);
         }
     }
 
diff --git a/core/src/main/java/com/netflix/conductor/core/events/DefaultEventProcessor.java b/core/src/main/java/com/netflix/conductor/core/events/DefaultEventProcessor.java
index 19767c4780..13cfae3ff0 100644
--- a/core/src/main/java/com/netflix/conductor/core/events/DefaultEventProcessor.java
+++ b/core/src/main/java/com/netflix/conductor/core/events/DefaultEventProcessor.java
@@ -111,7 +111,7 @@ public DefaultEventProcessor(
 
     public void handle(ObservableQueue queue, Message msg) {
         List<EventExecution> transientFailures = null;
-        Boolean executionFailed = false;
+        boolean executionFailed = false;
         try {
             if (isEventMessageIndexingEnabled) {
                 executionService.addMessage(queue.getName(), msg);
@@ -155,7 +155,7 @@ protected List<EventExecution> executeEvent(String event, Message msg) throws Ex
             String evaluatorType = eventHandler.getEvaluatorType();
             // Set default to true so that if condition is not specified, it falls through
             // to process the event.
-            Boolean success = true;
+            boolean success = true;
             if (StringUtils.isNotEmpty(condition) && evaluators.get(evaluatorType) != null) {
                 Object result =
                         evaluators
@@ -267,6 +267,7 @@ protected EventExecution execute(EventExecution eventExecution, Action action, O
                     eventExecution.getMessageId(),
                     payload);
 
+            // TODO: Switch to @Retryable annotation on SimpleActionProcessor.execute()
             Map<String, Object> output =
                     retryTemplate.execute(
                             context ->
diff --git a/core/src/main/java/com/netflix/conductor/core/events/queue/DefaultEventQueueProcessor.java b/core/src/main/java/com/netflix/conductor/core/events/queue/DefaultEventQueueProcessor.java
index 835d18c3ab..78abf836b8 100644
--- a/core/src/main/java/com/netflix/conductor/core/events/queue/DefaultEventQueueProcessor.java
+++ b/core/src/main/java/com/netflix/conductor/core/events/queue/DefaultEventQueueProcessor.java
@@ -22,8 +22,7 @@
 
 import com.netflix.conductor.common.metadata.tasks.Task;
 import com.netflix.conductor.common.metadata.tasks.TaskResult;
-import com.netflix.conductor.core.exception.ApplicationException;
-import com.netflix.conductor.core.exception.ApplicationException.Code;
+import com.netflix.conductor.core.exception.NotFoundException;
 import com.netflix.conductor.core.execution.WorkflowExecutor;
 import com.netflix.conductor.model.TaskModel;
 import com.netflix.conductor.model.TaskModel.Status;
@@ -154,14 +153,10 @@ private void startMonitor(Status status, ObservableQueue queue) {
                             } catch (JsonParseException e) {
                                 LOGGER.error("Bad message? : {} ", msg, e);
                                 queue.ack(Collections.singletonList(msg));
-
-                            } catch (ApplicationException e) {
-                                if (e.getCode().equals(Code.NOT_FOUND)) {
-                                    LOGGER.error(
-                                            "Workflow ID specified is not valid for this environment");
-                                    queue.ack(Collections.singletonList(msg));
-                                }
-                                LOGGER.error("Error processing message: {}", msg, e);
+                            } catch (NotFoundException nfe) {
+                                LOGGER.error(
+                                        "Workflow ID specified is not valid for this environment");
+                                queue.ack(Collections.singletonList(msg));
                             } catch (Exception e) {
                                 LOGGER.error("Error processing message: {}", msg, e);
                             }
diff --git a/core/src/main/java/com/netflix/conductor/core/exception/ApplicationException.java b/core/src/main/java/com/netflix/conductor/core/exception/ApplicationException.java
deleted file mode 100644
index f1a086d403..0000000000
--- a/core/src/main/java/com/netflix/conductor/core/exception/ApplicationException.java
+++ /dev/null
@@ -1,90 +0,0 @@
-/*
- * Copyright 2022 Netflix, Inc.
- * <p>
- * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
- * the License. You may obtain a copy of the License at
- * <p>
- * http://www.apache.org/licenses/LICENSE-2.0
- * <p>
- * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
- * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
- * specific language governing permissions and limitations under the License.
- */
-package com.netflix.conductor.core.exception;
-
-import java.io.ByteArrayOutputStream;
-import java.io.PrintStream;
-import java.util.HashMap;
-import java.util.LinkedHashMap;
-import java.util.Map;
-
-public class ApplicationException extends RuntimeException {
-
-    public enum Code {
-        INVALID_INPUT(400),
-        INTERNAL_ERROR(500),
-        NOT_FOUND(404),
-        CONFLICT(409),
-        UNAUTHORIZED(403),
-        BACKEND_ERROR(500);
-
-        private final int statusCode;
-
-        Code(int statusCode) {
-            this.statusCode = statusCode;
-        }
-
-        public int getStatusCode() {
-            return statusCode;
-        }
-    }
-
-    private final Code code;
-
-    public boolean isRetryable() {
-        return this.code == Code.BACKEND_ERROR;
-    }
-
-    public ApplicationException(String msg, Throwable t) {
-        this(Code.INTERNAL_ERROR, msg, t);
-    }
-
-    public ApplicationException(Code code, String msg, Throwable t) {
-        super(code + " - " + msg, t);
-        this.code = code;
-    }
-
-    public ApplicationException(Code code, Throwable t) {
-        super(code.name(), t);
-        this.code = code;
-    }
-
-    public ApplicationException(Code code, String message) {
-        super(message);
-        this.code = code;
-    }
-
-    public int getHttpStatusCode() {
-        return this.code.getStatusCode();
-    }
-
-    public Code getCode() {
-        return this.code;
-    }
-
-    public String getTrace() {
-        ByteArrayOutputStream baos = new ByteArrayOutputStream();
-        PrintStream ps = new PrintStream(baos);
-        this.printStackTrace(ps);
-        ps.flush();
-        return baos.toString();
-    }
-
-    public Map<String, Object> toMap() {
-        HashMap<String, Object> map = new LinkedHashMap<>();
-        map.put("code", code.name());
-        map.put("message", super.getMessage());
-        map.put("retryable", isRetryable());
-        return map;
-    }
-}
diff --git a/core/src/main/java/com/netflix/conductor/core/exception/ConflictException.java b/core/src/main/java/com/netflix/conductor/core/exception/ConflictException.java
new file mode 100644
index 0000000000..7c718ed59c
--- /dev/null
+++ b/core/src/main/java/com/netflix/conductor/core/exception/ConflictException.java
@@ -0,0 +1,28 @@
+/*
+ * Copyright 2022 Netflix, Inc.
+ * <p>
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ * <p>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p>
+ * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
+ * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations under the License.
+ */
+package com.netflix.conductor.core.exception;
+
+public class ConflictException extends RuntimeException {
+
+    public ConflictException(String message) {
+        super(message);
+    }
+
+    public ConflictException(String message, Object... args) {
+        super(String.format(message, args));
+    }
+
+    public ConflictException(String message, Throwable cause) {
+        super(message, cause);
+    }
+}
diff --git a/core/src/main/java/com/netflix/conductor/core/exception/NonTransientException.java b/core/src/main/java/com/netflix/conductor/core/exception/NonTransientException.java
new file mode 100644
index 0000000000..4af05633f9
--- /dev/null
+++ b/core/src/main/java/com/netflix/conductor/core/exception/NonTransientException.java
@@ -0,0 +1,24 @@
+/*
+ * Copyright 2022 Netflix, Inc.
+ * <p>
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ * <p>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p>
+ * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
+ * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations under the License.
+ */
+package com.netflix.conductor.core.exception;
+
+public class NonTransientException extends RuntimeException {
+
+    public NonTransientException(String message) {
+        super(message);
+    }
+
+    public NonTransientException(String message, Throwable cause) {
+        super(message, cause);
+    }
+}
diff --git a/core/src/main/java/com/netflix/conductor/core/exception/NotFoundException.java b/core/src/main/java/com/netflix/conductor/core/exception/NotFoundException.java
new file mode 100644
index 0000000000..a89b7beed9
--- /dev/null
+++ b/core/src/main/java/com/netflix/conductor/core/exception/NotFoundException.java
@@ -0,0 +1,28 @@
+/*
+ * Copyright 2022 Netflix, Inc.
+ * <p>
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ * <p>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p>
+ * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
+ * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations under the License.
+ */
+package com.netflix.conductor.core.exception;
+
+public class NotFoundException extends RuntimeException {
+
+    public NotFoundException(String message) {
+        super(message);
+    }
+
+    public NotFoundException(String message, Object... args) {
+        super(String.format(message, args));
+    }
+
+    public NotFoundException(String message, Throwable cause) {
+        super(message, cause);
+    }
+}
diff --git a/core/src/main/java/com/netflix/conductor/core/exception/TransientException.java b/core/src/main/java/com/netflix/conductor/core/exception/TransientException.java
new file mode 100644
index 0000000000..87cc9d852e
--- /dev/null
+++ b/core/src/main/java/com/netflix/conductor/core/exception/TransientException.java
@@ -0,0 +1,24 @@
+/*
+ * Copyright 2022 Netflix, Inc.
+ * <p>
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ * <p>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p>
+ * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
+ * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations under the License.
+ */
+package com.netflix.conductor.core.exception;
+
+public class TransientException extends RuntimeException {
+
+    public TransientException(String message) {
+        super(message);
+    }
+
+    public TransientException(String message, Throwable cause) {
+        super(message, cause);
+    }
+}
diff --git a/core/src/main/java/com/netflix/conductor/core/execution/WorkflowExecutor.java b/core/src/main/java/com/netflix/conductor/core/execution/WorkflowExecutor.java
index 63b8dafc6f..b7baee3f84 100644
--- a/core/src/main/java/com/netflix/conductor/core/execution/WorkflowExecutor.java
+++ b/core/src/main/java/com/netflix/conductor/core/execution/WorkflowExecutor.java
@@ -34,9 +34,11 @@
 import com.netflix.conductor.core.WorkflowContext;
 import com.netflix.conductor.core.config.ConductorProperties;
 import com.netflix.conductor.core.dal.ExecutionDAOFacade;
-import com.netflix.conductor.core.exception.ApplicationException;
-import com.netflix.conductor.core.exception.ApplicationException.Code;
+import com.netflix.conductor.core.exception.ConflictException;
+import com.netflix.conductor.core.exception.NonTransientException;
+import com.netflix.conductor.core.exception.NotFoundException;
 import com.netflix.conductor.core.exception.TerminateWorkflowException;
+import com.netflix.conductor.core.exception.TransientException;
 import com.netflix.conductor.core.execution.tasks.SystemTaskRegistry;
 import com.netflix.conductor.core.execution.tasks.Terminate;
 import com.netflix.conductor.core.execution.tasks.WorkflowSystemTask;
@@ -53,7 +55,6 @@
 import com.netflix.conductor.model.WorkflowModel;
 import com.netflix.conductor.service.ExecutionLockService;
 
-import static com.netflix.conductor.core.exception.ApplicationException.Code.*;
 import static com.netflix.conductor.core.utils.Utils.DECIDER_QUEUE;
 import static com.netflix.conductor.model.TaskModel.Status.*;
 
@@ -120,9 +121,6 @@ public WorkflowExecutor(
         this.systemTaskRegistry = systemTaskRegistry;
     }
 
-    /**
-     * @throws ApplicationException
-     */
     public String startWorkflow(
             String name,
             Integer version,
@@ -133,9 +131,6 @@ public String startWorkflow(
                 name, version, correlationId, input, externalInputPayloadStoragePath, null);
     }
 
-    /**
-     * @throws ApplicationException
-     */
     public String startWorkflow(
             String name,
             Integer version,
@@ -153,9 +148,6 @@ public String startWorkflow(
                 null);
     }
 
-    /**
-     * @throws ApplicationException
-     */
     public String startWorkflow(
             String name,
             Integer version,
@@ -174,9 +166,6 @@ public String startWorkflow(
                 event);
     }
 
-    /**
-     * @throws ApplicationException
-     */
     public String startWorkflow(
             String name,
             Integer version,
@@ -198,9 +187,6 @@ public String startWorkflow(
                 null);
     }
 
-    /**
-     * @throws ApplicationException
-     */
     public String startWorkflow(
             String name,
             Integer version,
@@ -220,9 +206,6 @@ public String startWorkflow(
                 taskToDomain);
     }
 
-    /**
-     * @throws ApplicationException
-     */
     public String startWorkflow(
             String name,
             Integer version,
@@ -245,9 +228,6 @@ public String startWorkflow(
                 taskToDomain);
     }
 
-    /**
-     * @throws ApplicationException
-     */
     public String startWorkflow(
             String name,
             Integer version,
@@ -269,9 +249,6 @@ public String startWorkflow(
                 null);
     }
 
-    /**
-     * @throws ApplicationException
-     */
     public String startWorkflow(
             WorkflowDef workflowDefinition,
             Map<String, Object> workflowInput,
@@ -289,9 +266,6 @@ public String startWorkflow(
                 taskToDomain);
     }
 
-    /**
-     * @throws ApplicationException
-     */
     public String startWorkflow(
             WorkflowDef workflowDefinition,
             Map<String, Object> workflowInput,
@@ -312,9 +286,6 @@ public String startWorkflow(
                 taskToDomain);
     }
 
-    /**
-     * @throws ApplicationException
-     */
     public String startWorkflow(
             String name,
             Integer version,
@@ -338,9 +309,6 @@ public String startWorkflow(
                 taskToDomain);
     }
 
-    /**
-     * @throws ApplicationException
-     */
     public String startWorkflow(
             String name,
             Integer version,
@@ -367,9 +335,6 @@ public String startWorkflow(
                 taskToDomain);
     }
 
-    /**
-     * @throws ApplicationException if validation fails
-     */
     public String startWorkflow(
             WorkflowDef workflowDefinition,
             Map<String, Object> workflowInput,
@@ -445,8 +410,7 @@ public String startWorkflow(
      */
     private void createWorkflow(WorkflowModel workflow) {
         if (!executionLockService.acquireLock(workflow.getWorkflowId())) {
-            throw new ApplicationException(
-                    BACKEND_ERROR, "Error acquiring lock when creating workflow: {}");
+            throw new TransientException("Error acquiring lock when creating workflow: {}");
         }
         try {
             executionDAOFacade.createWorkflow(workflow);
@@ -462,7 +426,7 @@ private void createWorkflow(WorkflowModel workflow) {
     /**
      * Performs validations for starting a workflow
      *
-     * @throws ApplicationException if the validation fails
+     * @throws IllegalArgumentException if the validation fails.
      */
     private void validateWorkflow(
             WorkflowDef workflowDef,
@@ -473,8 +437,7 @@ private void validateWorkflow(
             if (workflowInput == null && StringUtils.isBlank(externalStoragePath)) {
                 LOGGER.error(
                         "The input for the workflow '{}' cannot be NULL", workflowDef.getName());
-                throw new ApplicationException(
-                        INVALID_INPUT, "NULL input passed when starting workflow");
+                throw new IllegalArgumentException("NULL input passed when starting workflow");
             }
         } catch (Exception e) {
             Monitors.recordWorkflowStartError(
@@ -485,13 +448,13 @@ private void validateWorkflow(
 
     /**
      * @param workflowId the id of the workflow for which task callbacks are to be reset
-     * @throws ApplicationException if the workflow is in terminal state
+     * @throws ConflictException if the workflow is in terminal state
      */
     public void resetCallbacksForWorkflow(String workflowId) {
         WorkflowModel workflow = executionDAOFacade.getWorkflowModel(workflowId, true);
         if (workflow.getStatus().isTerminal()) {
-            throw new ApplicationException(
-                    CONFLICT, "Workflow is in terminal state. Status =" + workflow.getStatus());
+            throw new ConflictException(
+                    "Workflow is in terminal state. Status = %s", workflow.getStatus());
         }
 
         // Get SIMPLE tasks in SCHEDULED state that have callbackAfterSeconds > 0 and set the
@@ -520,8 +483,8 @@ public String rerun(RerunWorkflowRequest request) {
                 request.getTaskInput(),
                 request.getWorkflowInput(),
                 request.getCorrelationId())) {
-            throw new ApplicationException(
-                    INVALID_INPUT, "Task " + request.getReRunFromTaskId() + " not found");
+            throw new IllegalArgumentException(
+                    "Task " + request.getReRunFromTaskId() + " not found");
         }
         return request.getReRunFromWorkflowId();
     }
@@ -530,12 +493,9 @@ public String rerun(RerunWorkflowRequest request) {
      * @param workflowId the id of the workflow to be restarted
      * @param useLatestDefinitions if true, use the latest workflow and task definitions upon
      *     restart
-     * @throws ApplicationException in the following cases:
-     *     <ul>
-     *       <li>Workflow is not in a terminal state
-     *       <li>Workflow definition is not found
-     *       <li>Workflow is deemed non-restartable as per workflow definition
-     *     </ul>
+     * @throws ConflictException Workflow is not in a terminal state.
+     * @throws NotFoundException Workflow definition is not found or Workflow is deemed
+     *     non-restartable as per workflow definition.
      */
     public void restart(String workflowId, boolean useLatestDefinitions) {
         WorkflowModel workflow = executionDAOFacade.getWorkflowModel(workflowId, true);
@@ -544,7 +504,7 @@ public void restart(String workflowId, boolean useLatestDefinitions) {
                     String.format(
                             "Workflow: %s is not in terminal state, unable to restart.", workflow);
             LOGGER.error(errorMsg);
-            throw new ApplicationException(CONFLICT, errorMsg);
+            throw new ConflictException(errorMsg);
         }
 
         WorkflowDef workflowDef;
@@ -554,11 +514,9 @@ public void restart(String workflowId, boolean useLatestDefinitions) {
                             .getLatestWorkflowDef(workflow.getWorkflowName())
                             .orElseThrow(
                                     () ->
-                                            new ApplicationException(
-                                                    NOT_FOUND,
-                                                    String.format(
-                                                            "Unable to find latest definition for %s",
-                                                            workflowId)));
+                                            new NotFoundException(
+                                                    "Unable to find latest definition for %s",
+                                                    workflowId));
             workflow.setWorkflowDefinition(workflowDef);
         } else {
             workflowDef =
@@ -571,11 +529,9 @@ public void restart(String workflowId, boolean useLatestDefinitions) {
                                                             workflow.getWorkflowVersion())
                                                     .orElseThrow(
                                                             () ->
-                                                                    new ApplicationException(
-                                                                            NOT_FOUND,
-                                                                            String.format(
-                                                                                    "Unable to find definition for %s",
-                                                                                    workflowId))));
+                                                                    new NotFoundException(
+                                                                            "Unable to find definition for %s",
+                                                                            workflowId)));
         }
 
         if (!workflowDef.isRestartable()
@@ -584,8 +540,7 @@ public void restart(String workflowId, boolean useLatestDefinitions) {
                                 WorkflowModel.Status
                                         .COMPLETED)) { // Can only restart non-completed workflows
             // when the configuration is set to false
-            throw new ApplicationException(
-                    CONFLICT, String.format("Workflow: %s is non-restartable", workflow));
+            throw new NotFoundException("Workflow: %s is non-restartable", workflow);
         }
 
         // Reset the workflow in the primary datastore and remove from indexer; then re-create it
@@ -627,11 +582,11 @@ public void restart(String workflowId, boolean useLatestDefinitions) {
     public void retry(String workflowId, boolean resumeSubworkflowTasks) {
         WorkflowModel workflow = executionDAOFacade.getWorkflowModel(workflowId, true);
         if (!workflow.getStatus().isTerminal()) {
-            throw new ApplicationException(
-                    CONFLICT, "Workflow is still running.  status=" + workflow.getStatus());
+            throw new NotFoundException(
+                    "Workflow is still running.  status=%s", workflow.getStatus());
         }
         if (workflow.getTasks().isEmpty()) {
-            throw new ApplicationException(CONFLICT, "Workflow has not started yet");
+            throw new ConflictException("Workflow has not started yet");
         }
 
         if (resumeSubworkflowTasks) {
@@ -725,8 +680,7 @@ private void retry(WorkflowModel workflow) {
         // it may not have any unsuccessful tasks that can be retried
         if (retriableMap.values().size() == 0
                 && workflow.getStatus() != WorkflowModel.Status.TIMED_OUT) {
-            throw new ApplicationException(
-                    CONFLICT,
+            throw new ConflictException(
                     "There are no retryable tasks! Use restart if you want to attempt entire workflow execution again.");
         }
 
@@ -867,7 +821,7 @@ private void endExecution(WorkflowModel workflow) {
 
     /**
      * @param workflow the workflow to be completed
-     * @throws ApplicationException if workflow is not in terminal state
+     * @throws ConflictException if workflow is already in terminal state.
      */
     @VisibleForTesting
     WorkflowModel completeWorkflow(WorkflowModel workflow) {
@@ -885,7 +839,7 @@ WorkflowModel completeWorkflow(WorkflowModel workflow) {
             String msg =
                     "Workflow is already in terminal state. Current status: "
                             + workflow.getStatus();
-            throw new ApplicationException(CONFLICT, msg);
+            throw new ConflictException(msg);
         }
 
         // FIXME Backwards compatibility for legacy workflows already running.
@@ -935,7 +889,7 @@ WorkflowModel completeWorkflow(WorkflowModel workflow) {
     public void terminateWorkflow(String workflowId, String reason) {
         WorkflowModel workflow = executionDAOFacade.getWorkflowModel(workflowId, true);
         if (WorkflowModel.Status.COMPLETED.equals(workflow.getStatus())) {
-            throw new ApplicationException(CONFLICT, "Cannot terminate a COMPLETED workflow.");
+            throw new ConflictException("Cannot terminate a COMPLETED workflow.");
         }
         workflow.setStatus(WorkflowModel.Status.TERMINATED);
         terminateWorkflow(workflow, reason, null);
@@ -1062,8 +1016,7 @@ public WorkflowModel terminateWorkflow(
 
             List<String> erroredTasks = cancelNonTerminalTasks(workflow);
             if (!erroredTasks.isEmpty()) {
-                throw new ApplicationException(
-                        Code.INTERNAL_ERROR,
+                throw new NonTransientException(
                         String.format(
                                 "Error canceling system tasks: %s",
                                 String.join(",", erroredTasks)));
@@ -1076,13 +1029,13 @@ public WorkflowModel terminateWorkflow(
     }
 
     /**
-     * @param taskResult the task result to be updated
-     * @throws ApplicationException
+     * @param taskResult the task result to be updated.
+     * @throws IllegalArgumentException if the {@link TaskResult} is null.
+     * @throws NotFoundException if the Task is not found.
      */
     public void updateTask(TaskResult taskResult) {
         if (taskResult == null) {
-            throw new ApplicationException(
-                    ApplicationException.Code.INVALID_INPUT, "Task object is null");
+            throw new IllegalArgumentException("Task object is null");
         }
 
         String workflowId = taskResult.getWorkflowInstanceId();
@@ -1099,10 +1052,9 @@ public void updateTask(TaskResult taskResult) {
                 Optional.ofNullable(executionDAOFacade.getTaskModel(taskResult.getTaskId()))
                         .orElseThrow(
                                 () ->
-                                        new ApplicationException(
-                                                ApplicationException.Code.NOT_FOUND,
-                                                "No such task found by id: "
-                                                        + taskResult.getTaskId()));
+                                        new NotFoundException(
+                                                "No such task found by id: %s",
+                                                taskResult.getTaskId()));
 
         LOGGER.debug("Task: {} belonging to Workflow {} being updated", task, workflowInstance);
 
@@ -1209,7 +1161,7 @@ public void updateTask(TaskResult taskResult) {
                     LOGGER.error(errorMsg, e);
                     Monitors.recordTaskQueueOpError(
                             task.getTaskType(), workflowInstance.getWorkflowName());
-                    throw new ApplicationException(ApplicationException.Code.BACKEND_ERROR, e);
+                    throw new TransientException(errorMsg, e);
                 }
                 break;
             default:
@@ -1226,7 +1178,7 @@ public void updateTask(TaskResult taskResult) {
                             task.getTaskId(), workflowId);
             LOGGER.error(errorMsg, e);
             Monitors.recordTaskUpdateError(task.getTaskType(), workflowInstance.getWorkflowName());
-            throw new ApplicationException(ApplicationException.Code.BACKEND_ERROR, e);
+            throw new TransientException(errorMsg, e);
         }
 
         taskResult.getLogs().forEach(taskExecLog -> taskExecLog.setTaskId(task.getTaskId()));
@@ -1286,7 +1238,6 @@ private boolean _decide(String workflowId) {
     /**
      * @param workflowId ID of the workflow to evaluate the state for
      * @return true if the workflow has completed (success or failed), false otherwise.
-     * @throws ApplicationException If there was an error - caller should retry in this case.
      */
     public boolean decide(String workflowId) {
         if (!executionLockService.acquireLock(workflowId)) {
@@ -1399,8 +1350,7 @@ private Optional<TaskModel> findChangedSubWorkflowTask(WorkflowModel workflow) {
                                                         workflow.getWorkflowVersion())
                                                 .orElseThrow(
                                                         () ->
-                                                                new ApplicationException(
-                                                                        BACKEND_ERROR,
+                                                                new TransientException(
                                                                         "Workflow Definition is not found")));
         if (workflowDef.containsType(TaskType.TASK_TYPE_SUB_WORKFLOW)
                 || workflow.getWorkflowDefinition()
@@ -1478,7 +1428,7 @@ List<TaskModel> dedupAndAddTasks(WorkflowModel workflow, List<TaskModel> tasks)
     }
 
     /**
-     * @throws ApplicationException if the workflow cannot be paused
+     * @throws ConflictException if the workflow is in terminal state.
      */
     public void pauseWorkflow(String workflowId) {
         try {
@@ -1486,9 +1436,9 @@ public void pauseWorkflow(String workflowId) {
             WorkflowModel.Status status = WorkflowModel.Status.PAUSED;
             WorkflowModel workflow = executionDAOFacade.getWorkflowModel(workflowId, false);
             if (workflow.getStatus().isTerminal()) {
-                throw new ApplicationException(
-                        CONFLICT,
-                        "Workflow id " + workflowId + " has ended, status cannot be updated.");
+                throw new ConflictException(
+                        "Workflow %s has ended, status cannot be updated.",
+                        workflow.toShortString());
             }
             if (workflow.getStatus().equals(status)) {
                 return; // Already paused!
@@ -1743,8 +1693,8 @@ boolean scheduleTask(WorkflowModel workflow, List<TaskModel> tasks) {
             for (TaskModel task : systemTasks) {
                 WorkflowSystemTask workflowSystemTask = systemTaskRegistry.get(task.getTaskType());
                 if (workflowSystemTask == null) {
-                    throw new ApplicationException(
-                            NOT_FOUND, "No system task found by name " + task.getTaskType());
+                    throw new NotFoundException(
+                            "No system task found by name %s", task.getTaskType());
                 }
                 if (task.getStatus() != null
                         && !task.getStatus().isTerminal()
@@ -1761,8 +1711,7 @@ boolean scheduleTask(WorkflowModel workflow, List<TaskModel> tasks) {
                                         task.getTaskType(),
                                         task.getTaskId(),
                                         task.getTaskDefName());
-                        throw new ApplicationException(
-                                ApplicationException.Code.INTERNAL_ERROR, errorMsg, e);
+                        throw new NonTransientException(errorMsg, e);
                     }
                     startedSystemTasks = true;
                     executionDAOFacade.updateTask(task);
@@ -1844,7 +1793,7 @@ private boolean rerunWF(
                     String.format(
                             "Workflow: %s is not in terminal state, unable to rerun.", workflow);
             LOGGER.error(errorMsg);
-            throw new ApplicationException(CONFLICT, errorMsg);
+            throw new ConflictException(errorMsg);
         }
         updateAndPushParents(workflow, "reran");
 
diff --git a/core/src/main/java/com/netflix/conductor/core/execution/tasks/Event.java b/core/src/main/java/com/netflix/conductor/core/execution/tasks/Event.java
index 5e9a9aef4c..c1c50db6ef 100644
--- a/core/src/main/java/com/netflix/conductor/core/execution/tasks/Event.java
+++ b/core/src/main/java/com/netflix/conductor/core/execution/tasks/Event.java
@@ -24,7 +24,7 @@
 import com.netflix.conductor.core.events.EventQueues;
 import com.netflix.conductor.core.events.queue.Message;
 import com.netflix.conductor.core.events.queue.ObservableQueue;
-import com.netflix.conductor.core.exception.ApplicationException;
+import com.netflix.conductor.core.exception.TransientException;
 import com.netflix.conductor.core.execution.WorkflowExecutor;
 import com.netflix.conductor.core.utils.ParametersUtils;
 import com.netflix.conductor.model.TaskModel;
@@ -72,20 +72,10 @@ public void start(WorkflowModel workflow, TaskModel task, WorkflowExecutor workf
                     isAsyncComplete(task)
                             ? TaskModel.Status.IN_PROGRESS
                             : TaskModel.Status.COMPLETED);
-        } catch (ApplicationException ae) {
-            if (ae.isRetryable()) {
-                LOGGER.info(
-                        "A transient backend error happened when task {} tried to publish an event.",
-                        task.getTaskId());
-            } else {
-                task.setStatus(TaskModel.Status.FAILED);
-                task.setReasonForIncompletion(ae.getMessage());
-                LOGGER.error(
-                        "Error executing task: {}, workflow: {}",
-                        task.getTaskId(),
-                        workflow.getWorkflowId(),
-                        ae);
-            }
+        } catch (TransientException te) {
+            LOGGER.info(
+                    "A transient backend error happened when task {} tried to publish an event.",
+                    task.getTaskId());
         } catch (JsonProcessingException jpe) {
             task.setStatus(TaskModel.Status.FAILED);
             task.setReasonForIncompletion("Error serializing JSON payload: " + jpe.getMessage());
diff --git a/core/src/main/java/com/netflix/conductor/core/execution/tasks/SetVariable.java b/core/src/main/java/com/netflix/conductor/core/execution/tasks/SetVariable.java
index 2e84742148..2db2a9a18f 100644
--- a/core/src/main/java/com/netflix/conductor/core/execution/tasks/SetVariable.java
+++ b/core/src/main/java/com/netflix/conductor/core/execution/tasks/SetVariable.java
@@ -23,7 +23,7 @@
 import org.springframework.stereotype.Component;
 
 import com.netflix.conductor.core.config.ConductorProperties;
-import com.netflix.conductor.core.exception.ApplicationException;
+import com.netflix.conductor.core.exception.NonTransientException;
 import com.netflix.conductor.core.execution.WorkflowExecutor;
 import com.netflix.conductor.model.TaskModel;
 import com.netflix.conductor.model.WorkflowModel;
@@ -69,7 +69,8 @@ private boolean validateVariablesSize(
         } catch (IOException e) {
             LOGGER.error(
                     "Unable to validate variables payload size of workflow: {}", workflowId, e);
-            throw new ApplicationException(ApplicationException.Code.INTERNAL_ERROR, e);
+            throw new NonTransientException(
+                    "Unable to validate variables payload size of workflow: " + workflowId, e);
         }
     }
 
diff --git a/core/src/main/java/com/netflix/conductor/core/execution/tasks/StartWorkflow.java b/core/src/main/java/com/netflix/conductor/core/execution/tasks/StartWorkflow.java
index 59abde2a82..8e89441410 100644
--- a/core/src/main/java/com/netflix/conductor/core/execution/tasks/StartWorkflow.java
+++ b/core/src/main/java/com/netflix/conductor/core/execution/tasks/StartWorkflow.java
@@ -22,7 +22,7 @@
 import org.springframework.stereotype.Component;
 
 import com.netflix.conductor.common.metadata.workflow.StartWorkflowRequest;
-import com.netflix.conductor.core.exception.ApplicationException;
+import com.netflix.conductor.core.exception.TransientException;
 import com.netflix.conductor.core.execution.WorkflowExecutor;
 import com.netflix.conductor.model.TaskModel;
 import com.netflix.conductor.model.WorkflowModel;
@@ -67,30 +67,21 @@ public void start(
             String workflowId = startWorkflow(request, workflowExecutor);
             taskModel.addOutput(WORKFLOW_ID, workflowId);
             taskModel.setStatus(COMPLETED);
-        } catch (ApplicationException ae) {
-            if (ae.isRetryable()) {
-                LOGGER.info(
-                        "A transient backend error happened when task {} in {} tried to start workflow {}.",
-                        taskModel.getTaskId(),
-                        workflow.toShortString(),
-                        request.getName());
-            } else {
-                taskModel.setStatus(FAILED);
-                taskModel.setReasonForIncompletion(ae.getMessage());
-                LOGGER.error(
-                        "Error starting workflow: {} from workflow: {}",
-                        request.getName(),
-                        workflow.toShortString(),
-                        ae);
-            }
-        } catch (Exception e) {
+        } catch (TransientException te) {
+            LOGGER.info(
+                    "A transient backend error happened when task {} in {} tried to start workflow {}.",
+                    taskModel.getTaskId(),
+                    workflow.toShortString(),
+                    request.getName());
+        } catch (Exception ae) {
+
             taskModel.setStatus(FAILED);
-            taskModel.setReasonForIncompletion(e.getMessage());
+            taskModel.setReasonForIncompletion(ae.getMessage());
             LOGGER.error(
                     "Error starting workflow: {} from workflow: {}",
                     request.getName(),
                     workflow.toShortString(),
-                    e);
+                    ae);
         }
     }
 
diff --git a/core/src/main/java/com/netflix/conductor/core/execution/tasks/SubWorkflow.java b/core/src/main/java/com/netflix/conductor/core/execution/tasks/SubWorkflow.java
index 75995832d6..baf0844b4c 100644
--- a/core/src/main/java/com/netflix/conductor/core/execution/tasks/SubWorkflow.java
+++ b/core/src/main/java/com/netflix/conductor/core/execution/tasks/SubWorkflow.java
@@ -20,7 +20,8 @@
 import org.springframework.stereotype.Component;
 
 import com.netflix.conductor.common.metadata.workflow.WorkflowDef;
-import com.netflix.conductor.core.exception.ApplicationException;
+import com.netflix.conductor.core.exception.NonTransientException;
+import com.netflix.conductor.core.exception.TransientException;
 import com.netflix.conductor.core.execution.WorkflowExecutor;
 import com.netflix.conductor.model.TaskModel;
 import com.netflix.conductor.model.WorkflowModel;
@@ -105,30 +106,21 @@ public void start(WorkflowModel workflow, TaskModel task, WorkflowExecutor workf
             // recursion by the time we update here.
             WorkflowModel subWorkflow = workflowExecutor.getWorkflow(subWorkflowId, false);
             updateTaskStatus(subWorkflow, task);
-        } catch (ApplicationException ae) {
-            if (ae.isRetryable()) {
-                LOGGER.info(
-                        "A transient backend error happened when task {} in {} tried to start sub workflow {}.",
-                        task.getTaskId(),
-                        workflow.toShortString(),
-                        name);
-            } else {
-                task.setStatus(TaskModel.Status.FAILED);
-                task.setReasonForIncompletion(ae.getMessage());
-                LOGGER.error(
-                        "Error starting sub workflow: {} from workflow: {}",
-                        name,
-                        workflow.toShortString(),
-                        ae);
-            }
-        } catch (Exception e) {
+        } catch (TransientException te) {
+            LOGGER.info(
+                    "A transient backend error happened when task {} in {} tried to start sub workflow {}.",
+                    task.getTaskId(),
+                    workflow.toShortString(),
+                    name);
+        } catch (Exception ae) {
+
             task.setStatus(TaskModel.Status.FAILED);
-            task.setReasonForIncompletion(e.getMessage());
+            task.setReasonForIncompletion(ae.getMessage());
             LOGGER.error(
                     "Error starting sub workflow: {} from workflow: {}",
                     name,
                     workflow.toShortString(),
-                    e);
+                    ae);
         }
     }
 
@@ -204,8 +196,7 @@ private void updateTaskStatus(WorkflowModel subworkflow, TaskModel task) {
                 task.setStatus(TaskModel.Status.TIMED_OUT);
                 break;
             default:
-                throw new ApplicationException(
-                        ApplicationException.Code.INTERNAL_ERROR,
+                throw new NonTransientException(
                         "Subworkflow status does not conform to relevant task status.");
         }
 
diff --git a/core/src/main/java/com/netflix/conductor/core/metadata/MetadataMapperService.java b/core/src/main/java/com/netflix/conductor/core/metadata/MetadataMapperService.java
index d632853200..7a825adac8 100644
--- a/core/src/main/java/com/netflix/conductor/core/metadata/MetadataMapperService.java
+++ b/core/src/main/java/com/netflix/conductor/core/metadata/MetadataMapperService.java
@@ -28,7 +28,7 @@
 import com.netflix.conductor.common.metadata.workflow.WorkflowDef;
 import com.netflix.conductor.common.metadata.workflow.WorkflowTask;
 import com.netflix.conductor.core.WorkflowContext;
-import com.netflix.conductor.core.exception.ApplicationException;
+import com.netflix.conductor.core.exception.NotFoundException;
 import com.netflix.conductor.core.exception.TerminateWorkflowException;
 import com.netflix.conductor.core.utils.Utils;
 import com.netflix.conductor.dao.MetadataDAO;
@@ -69,11 +69,8 @@ public WorkflowDef lookupForWorkflowDefinition(String name, Integer version) {
                             "There is no workflow defined with name {} and version {}",
                             name,
                             version);
-                    return new ApplicationException(
-                            ApplicationException.Code.NOT_FOUND,
-                            String.format(
-                                    "No such workflow defined. name=%s, version=%s",
-                                    name, version));
+                    return new NotFoundException(
+                            "No such workflow defined. name=%s, version=%s", name, version);
                 });
     }
 
@@ -176,8 +173,7 @@ private void checkNotEmptyDefinitions(WorkflowDef workflowDefinition) {
                     missingTaskDefinitionNames);
             Monitors.recordWorkflowStartError(
                     workflowDefinition.getName(), WorkflowContext.get().getClientApp());
-            throw new ApplicationException(
-                    ApplicationException.Code.INVALID_INPUT,
+            throw new IllegalArgumentException(
                     "Cannot find the task definitions for the following tasks used in workflow: "
                             + missingTaskDefinitionNames);
         }
diff --git a/core/src/main/java/com/netflix/conductor/core/reconciliation/WorkflowSweeper.java b/core/src/main/java/com/netflix/conductor/core/reconciliation/WorkflowSweeper.java
index 2d3c1eaa59..134130049f 100644
--- a/core/src/main/java/com/netflix/conductor/core/reconciliation/WorkflowSweeper.java
+++ b/core/src/main/java/com/netflix/conductor/core/reconciliation/WorkflowSweeper.java
@@ -23,7 +23,7 @@
 
 import com.netflix.conductor.core.WorkflowContext;
 import com.netflix.conductor.core.config.ConductorProperties;
-import com.netflix.conductor.core.exception.ApplicationException;
+import com.netflix.conductor.core.exception.NotFoundException;
 import com.netflix.conductor.core.execution.WorkflowExecutor;
 import com.netflix.conductor.dao.QueueDAO;
 import com.netflix.conductor.metrics.Monitors;
@@ -78,15 +78,11 @@ public void sweep(String workflowId) {
                 queueDAO.remove(DECIDER_QUEUE, workflowId);
                 return;
             }
-        } catch (ApplicationException e) {
-            if (e.getCode() == ApplicationException.Code.NOT_FOUND) {
-                queueDAO.remove(DECIDER_QUEUE, workflowId);
-                LOGGER.info(
-                        "Workflow NOT found for id:{}. Removed it from decider queue",
-                        workflowId,
-                        e);
-                return;
-            }
+        } catch (NotFoundException nfe) {
+            queueDAO.remove(DECIDER_QUEUE, workflowId);
+            LOGGER.info(
+                    "Workflow NOT found for id:{}. Removed it from decider queue", workflowId, nfe);
+            return;
         } catch (Exception e) {
             Monitors.error(CLASS_NAME, "sweep");
             LOGGER.error("Error running sweep for " + workflowId, e);
diff --git a/core/src/main/java/com/netflix/conductor/core/utils/ExternalPayloadStorageUtils.java b/core/src/main/java/com/netflix/conductor/core/utils/ExternalPayloadStorageUtils.java
index 53a2246e26..008c5202de 100644
--- a/core/src/main/java/com/netflix/conductor/core/utils/ExternalPayloadStorageUtils.java
+++ b/core/src/main/java/com/netflix/conductor/core/utils/ExternalPayloadStorageUtils.java
@@ -30,7 +30,7 @@
 import com.netflix.conductor.common.utils.ExternalPayloadStorage;
 import com.netflix.conductor.common.utils.ExternalPayloadStorage.PayloadType;
 import com.netflix.conductor.core.config.ConductorProperties;
-import com.netflix.conductor.core.exception.ApplicationException;
+import com.netflix.conductor.core.exception.NonTransientException;
 import com.netflix.conductor.core.exception.TerminateWorkflowException;
 import com.netflix.conductor.metrics.Monitors;
 import com.netflix.conductor.model.TaskModel;
@@ -62,7 +62,7 @@ public ExternalPayloadStorageUtils(
      *
      * @param path the relative path of the payload in the {@link ExternalPayloadStorage}
      * @return the payload object
-     * @throws ApplicationException in case of JSON parsing errors or download errors
+     * @throws NonTransientException in case of JSON parsing errors or download errors
      */
     @SuppressWarnings("unchecked")
     public Map<String, Object> downloadPayload(String path) {
@@ -71,7 +71,8 @@ public Map<String, Object> downloadPayload(String path) {
                     IOUtils.toString(inputStream, StandardCharsets.UTF_8), Map.class);
         } catch (IOException e) {
             LOGGER.error("Unable to download payload from external storage path: {}", path, e);
-            throw new ApplicationException(ApplicationException.Code.INTERNAL_ERROR, e);
+            throw new NonTransientException(
+                    "Unable to download payload from external storage path: " + path, e);
         }
     }
 
@@ -81,7 +82,7 @@ public Map<String, Object> downloadPayload(String path) {
      * @param entity the task or workflow for which the payload is to be verified and uploaded
      * @param payloadType the {@link PayloadType} of the payload
      * @param <T> {@link TaskModel} or {@link WorkflowModel}
-     * @throws ApplicationException in case of JSON parsing errors or upload errors
+     * @throws NonTransientException in case of JSON parsing errors or upload errors
      * @throws TerminateWorkflowException if the payload size is bigger than permissible limit as
      *     per {@link ConductorProperties}
      */
@@ -188,7 +189,8 @@ public <T> void verifyAndUpload(T entity, PayloadType payloadType) {
         } catch (IOException e) {
             LOGGER.error(
                     "Unable to upload payload to external storage for workflow: {}", workflowId, e);
-            throw new ApplicationException(ApplicationException.Code.INTERNAL_ERROR, e);
+            throw new NonTransientException(
+                    "Unable to upload payload to external storage for workflow: " + workflowId, e);
         }
     }
 
diff --git a/core/src/main/java/com/netflix/conductor/core/utils/Utils.java b/core/src/main/java/com/netflix/conductor/core/utils/Utils.java
index 537d1137a4..e81b3cf587 100644
--- a/core/src/main/java/com/netflix/conductor/core/utils/Utils.java
+++ b/core/src/main/java/com/netflix/conductor/core/utils/Utils.java
@@ -18,7 +18,7 @@
 
 import org.apache.commons.lang3.StringUtils;
 
-import com.netflix.conductor.core.exception.ApplicationException;
+import com.netflix.conductor.core.exception.TransientException;
 
 public class Utils {
 
@@ -56,7 +56,7 @@ public static List<String> convertStringToList(String inputStr) {
      *
      * @param condition a boolean expression
      * @param errorMessage The exception message use if the input condition is not valid
-     * @throws ApplicationException if input condition is not valid
+     * @throws IllegalArgumentException if input condition is not valid.
      */
     public static void checkArgument(boolean condition, String errorMessage) {
         if (!condition) {
@@ -64,51 +64,12 @@ public static void checkArgument(boolean condition, String errorMessage) {
         }
     }
 
-    /**
-     * This method checks if the collection is null or is empty.
-     *
-     * @param collection input of type {@link Collection}
-     * @param errorMessage The exception message use if the collection is empty or null
-     * @throws ApplicationException if input Collection is not valid
-     */
-    public static void checkNotNullOrEmpty(Collection<?> collection, String errorMessage) {
-        if (collection == null || collection.isEmpty()) {
-            throw new ApplicationException(ApplicationException.Code.INVALID_INPUT, errorMessage);
-        }
-    }
-
-    /**
-     * This method checks if the input map is valid or not.
-     *
-     * @param map input of type {@link Map}
-     * @param errorMessage The exception message use if the map is empty or null
-     * @throws ApplicationException if input map is not valid
-     */
-    public static void checkNotNullOrEmpty(Map<?, ?> map, String errorMessage) {
-        if (map == null || map.isEmpty()) {
-            throw new ApplicationException(ApplicationException.Code.INVALID_INPUT, errorMessage);
-        }
-    }
-
-    /**
-     * This method checks it the input string is null or empty.
-     *
-     * @param input input of type {@link String}
-     * @param errorMessage The exception message use if the string is empty or null
-     * @throws ApplicationException if input string is not valid
-     */
-    public static void checkNotNullOrEmpty(String input, String errorMessage) {
-        if (StringUtils.isEmpty(input)) {
-            throw new ApplicationException(ApplicationException.Code.INVALID_INPUT, errorMessage);
-        }
-    }
-
     /**
      * This method checks if the object is null or empty.
      *
-     * @param object input of type {@link Object}
-     * @param errorMessage The exception message use if the object is empty or null
-     * @throws ApplicationException if input object is not valid
+     * @param object input of type {@link Object}.
+     * @param errorMessage The exception message use if the object is empty or null.
+     * @throws NullPointerException if input object is not valid.
      */
     public static void checkNotNull(Object object, String errorMessage) {
         if (object == null) {
@@ -126,10 +87,7 @@ public static void checkNotNull(Object object, String errorMessage) {
      */
     public static boolean isTransientException(Throwable throwable) {
         if (throwable != null) {
-            return !((throwable instanceof UnsupportedOperationException)
-                    || (throwable instanceof ApplicationException
-                            && ((ApplicationException) throwable).getCode()
-                                    != ApplicationException.Code.BACKEND_ERROR));
+            return throwable instanceof TransientException;
         }
         return true;
     }
diff --git a/core/src/main/java/com/netflix/conductor/model/TaskModel.java b/core/src/main/java/com/netflix/conductor/model/TaskModel.java
index 94cc47b13c..0462a8cee0 100644
--- a/core/src/main/java/com/netflix/conductor/model/TaskModel.java
+++ b/core/src/main/java/com/netflix/conductor/model/TaskModel.java
@@ -126,8 +126,6 @@ public boolean isRetriable() {
 
     private Any outputMessage;
 
-    // id 31 is reserved
-
     private int rateLimitPerFrequency;
 
     private int rateLimitFrequencyInSeconds;
diff --git a/core/src/main/java/com/netflix/conductor/service/ExecutionService.java b/core/src/main/java/com/netflix/conductor/service/ExecutionService.java
index 97f95dbee8..bf7f7d731c 100644
--- a/core/src/main/java/com/netflix/conductor/service/ExecutionService.java
+++ b/core/src/main/java/com/netflix/conductor/service/ExecutionService.java
@@ -45,7 +45,7 @@
 import com.netflix.conductor.core.config.ConductorProperties;
 import com.netflix.conductor.core.dal.ExecutionDAOFacade;
 import com.netflix.conductor.core.events.queue.Message;
-import com.netflix.conductor.core.exception.ApplicationException;
+import com.netflix.conductor.core.exception.NotFoundException;
 import com.netflix.conductor.core.execution.WorkflowExecutor;
 import com.netflix.conductor.core.execution.tasks.SystemTaskRegistry;
 import com.netflix.conductor.core.utils.QueueUtils;
@@ -109,8 +109,7 @@ public List<Task> poll(String taskType, String workerId, int count, int timeoutI
     public List<Task> poll(
             String taskType, String workerId, String domain, int count, int timeoutInMilliSecond) {
         if (timeoutInMilliSecond > MAX_POLL_TIMEOUT_MS) {
-            throw new ApplicationException(
-                    ApplicationException.Code.INVALID_INPUT,
+            throw new IllegalArgumentException(
                     "Long Poll Timeout value cannot be more than 5 seconds");
         }
         String queueName = QueueUtils.getQueueName(taskType, domain, null, null);
@@ -305,9 +304,7 @@ public Integer getTaskQueueSize(String queueName) {
     public void removeTaskFromQueue(String taskId) {
         Task task = getTask(taskId);
         if (task == null) {
-            throw new ApplicationException(
-                    ApplicationException.Code.NOT_FOUND,
-                    String.format("No such task found by taskId: %s", taskId));
+            throw new NotFoundException("No such task found by taskId: %s", taskId);
         }
         queueDAO.remove(QueueUtils.getQueueName(task), taskId);
     }
diff --git a/core/src/main/java/com/netflix/conductor/service/MetadataServiceImpl.java b/core/src/main/java/com/netflix/conductor/service/MetadataServiceImpl.java
index 24ebd03083..6df42bb04f 100644
--- a/core/src/main/java/com/netflix/conductor/service/MetadataServiceImpl.java
+++ b/core/src/main/java/com/netflix/conductor/service/MetadataServiceImpl.java
@@ -23,8 +23,7 @@
 import com.netflix.conductor.common.metadata.workflow.WorkflowDef;
 import com.netflix.conductor.core.WorkflowContext;
 import com.netflix.conductor.core.config.ConductorProperties;
-import com.netflix.conductor.core.exception.ApplicationException;
-import com.netflix.conductor.core.exception.ApplicationException.Code;
+import com.netflix.conductor.core.exception.NotFoundException;
 import com.netflix.conductor.dao.EventHandlerDAO;
 import com.netflix.conductor.dao.MetadataDAO;
 import com.netflix.conductor.validations.ValidationContext;
@@ -67,8 +66,7 @@ public void registerTaskDef(List<TaskDef> taskDefinitions) {
     public void updateTaskDef(TaskDef taskDefinition) {
         TaskDef existing = metadataDAO.getTaskDef(taskDefinition.getName());
         if (existing == null) {
-            throw new ApplicationException(
-                    Code.NOT_FOUND, "No such task by name " + taskDefinition.getName());
+            throw new NotFoundException("No such task by name %s", taskDefinition.getName());
         }
         taskDefinition.setUpdatedBy(WorkflowContext.get().getClientApp());
         taskDefinition.setUpdateTime(System.currentTimeMillis());
@@ -96,8 +94,7 @@ public List<TaskDef> getTaskDefs() {
     public TaskDef getTaskDef(String taskType) {
         TaskDef taskDef = metadataDAO.getTaskDef(taskType);
         if (taskDef == null) {
-            throw new ApplicationException(
-                    Code.NOT_FOUND, String.format("No such taskType found by name: %s", taskType));
+            throw new NotFoundException("No such taskType found by name: %s", taskType);
         }
         return taskDef;
     }
@@ -135,11 +132,8 @@ public WorkflowDef getWorkflowDef(String name, Integer version) {
 
         return workflowDef.orElseThrow(
                 () ->
-                        new ApplicationException(
-                                Code.NOT_FOUND,
-                                String.format(
-                                        "No such workflow found by name: %s, version: %d",
-                                        name, version)));
+                        new NotFoundException(
+                                "No such workflow found by name: %s, version: %d", name, version));
     }
 
     /**
@@ -156,8 +150,7 @@ public List<WorkflowDef> getWorkflowDefs() {
 
     public void registerWorkflowDef(WorkflowDef workflowDef) {
         if (workflowDef.getName().contains(":")) {
-            throw new ApplicationException(
-                    Code.INVALID_INPUT,
+            throw new IllegalArgumentException(
                     "Workflow name cannot contain the following set of characters: ':'");
         }
         if (workflowDef.getSchemaVersion() < 1 || workflowDef.getSchemaVersion() > 2) {
diff --git a/core/src/main/java/com/netflix/conductor/service/TaskServiceImpl.java b/core/src/main/java/com/netflix/conductor/service/TaskServiceImpl.java
index 333b2e3469..ad05dc36b4 100644
--- a/core/src/main/java/com/netflix/conductor/service/TaskServiceImpl.java
+++ b/core/src/main/java/com/netflix/conductor/service/TaskServiceImpl.java
@@ -259,7 +259,11 @@ public Map<String, Integer> getTaskQueueSizes(List<String> taskTypes) {
     public Integer getTaskQueueSize(
             String taskType, String domain, String isolationGroupId, String executionNamespace) {
         String queueName =
-                QueueUtils.getQueueName(taskType, domain, isolationGroupId, executionNamespace);
+                QueueUtils.getQueueName(
+                        taskType,
+                        StringUtils.trimToNull(domain),
+                        StringUtils.trimToNull(isolationGroupId),
+                        StringUtils.trimToNull(executionNamespace));
 
         return executionService.getTaskQueueSize(queueName);
     }
diff --git a/core/src/main/java/com/netflix/conductor/service/WorkflowServiceImpl.java b/core/src/main/java/com/netflix/conductor/service/WorkflowServiceImpl.java
index f1a84a13dd..d8f90bd953 100644
--- a/core/src/main/java/com/netflix/conductor/service/WorkflowServiceImpl.java
+++ b/core/src/main/java/com/netflix/conductor/service/WorkflowServiceImpl.java
@@ -33,7 +33,7 @@
 import com.netflix.conductor.common.run.Workflow;
 import com.netflix.conductor.common.run.WorkflowSummary;
 import com.netflix.conductor.common.utils.ExternalPayloadStorage;
-import com.netflix.conductor.core.exception.ApplicationException;
+import com.netflix.conductor.core.exception.NotFoundException;
 import com.netflix.conductor.core.execution.WorkflowExecutor;
 import com.netflix.conductor.core.utils.Utils;
 
@@ -187,10 +187,8 @@ public String startWorkflow(
             Map<String, Object> input) {
         WorkflowDef workflowDef = metadataService.getWorkflowDef(name, version);
         if (workflowDef == null) {
-            throw new ApplicationException(
-                    ApplicationException.Code.NOT_FOUND,
-                    String.format(
-                            "No such workflow found by name: %s, version: %d", name, version));
+            throw new NotFoundException(
+                    "No such workflow found by name: %s, version: %d", name, version);
         }
         return workflowExecutor.startWorkflow(
                 workflowDef.getName(),
@@ -247,9 +245,7 @@ public Map<String, List<Workflow>> getWorkflows(
     public Workflow getExecutionStatus(String workflowId, boolean includeTasks) {
         Workflow workflow = executionService.getExecutionStatus(workflowId, includeTasks);
         if (workflow == null) {
-            throw new ApplicationException(
-                    ApplicationException.Code.NOT_FOUND,
-                    String.format("Workflow with Id: %s not found.", workflowId));
+            throw new NotFoundException("Workflow with id: %s not found.", workflowId);
         }
         return workflow;
     }
diff --git a/core/src/test/groovy/com/netflix/conductor/core/execution/tasks/EventSpec.groovy b/core/src/test/groovy/com/netflix/conductor/core/execution/tasks/EventSpec.groovy
index a8a4451e64..ad00742e35 100644
--- a/core/src/test/groovy/com/netflix/conductor/core/execution/tasks/EventSpec.groovy
+++ b/core/src/test/groovy/com/netflix/conductor/core/execution/tasks/EventSpec.groovy
@@ -16,7 +16,8 @@ import com.netflix.conductor.common.metadata.workflow.WorkflowDef
 import com.netflix.conductor.core.events.EventQueues
 import com.netflix.conductor.core.events.queue.Message
 import com.netflix.conductor.core.events.queue.ObservableQueue
-import com.netflix.conductor.core.exception.ApplicationException
+import com.netflix.conductor.core.exception.NonTransientException
+import com.netflix.conductor.core.exception.TransientException
 import com.netflix.conductor.core.utils.ParametersUtils
 import com.netflix.conductor.model.TaskModel
 import com.netflix.conductor.model.WorkflowModel
@@ -227,7 +228,7 @@ class EventSpec extends Specification {
         1 * parametersUtils.getTaskInputV2(_, workflow, task.taskId, _) >> ['sink': sinkValue]
         1 * eventQueues.getQueue(_) >> observableQueue
         // capture the Message object sent to the publish method. Event.start sends a list with one Message object
-        1 * observableQueue.publish(_) >> { throw new ApplicationException(ApplicationException.Code.BACKEND_ERROR, "transient error") }
+        1 * observableQueue.publish(_) >> { throw new TransientException("transient error") }
     }
 
     def "publishing to a queue throws a non-retryable ApplicationException"() {
@@ -246,7 +247,7 @@ class EventSpec extends Specification {
         1 * parametersUtils.getTaskInputV2(_, workflow, task.taskId, _) >> ['sink': sinkValue]
         1 * eventQueues.getQueue(_) >> observableQueue
         // capture the Message object sent to the publish method. Event.start sends a list with one Message object
-        1 * observableQueue.publish(_) >> { throw new ApplicationException(ApplicationException.Code.INTERNAL_ERROR, "fatal error") }
+        1 * observableQueue.publish(_) >> { throw new NonTransientException("fatal error") }
     }
 
     def "event task fails to convert the payload to json"() {
diff --git a/core/src/test/groovy/com/netflix/conductor/core/execution/tasks/StartWorkflowSpec.groovy b/core/src/test/groovy/com/netflix/conductor/core/execution/tasks/StartWorkflowSpec.groovy
index 7ef18baae1..dc3c045942 100644
--- a/core/src/test/groovy/com/netflix/conductor/core/execution/tasks/StartWorkflowSpec.groovy
+++ b/core/src/test/groovy/com/netflix/conductor/core/execution/tasks/StartWorkflowSpec.groovy
@@ -12,12 +12,12 @@
  */
 package com.netflix.conductor.core.execution.tasks
 
-
 import javax.validation.ConstraintViolation
 import javax.validation.Validator
 
 import com.netflix.conductor.common.config.ObjectMapperProvider
-import com.netflix.conductor.core.exception.ApplicationException
+import com.netflix.conductor.core.exception.NotFoundException
+import com.netflix.conductor.core.exception.TransientException
 import com.netflix.conductor.core.execution.WorkflowExecutor
 import com.netflix.conductor.model.TaskModel
 import com.netflix.conductor.model.WorkflowModel
@@ -91,7 +91,7 @@ class StartWorkflowSpec extends Specification {
 
         then:
         taskModel.status == SCHEDULED
-        1 * workflowExecutor.startWorkflow(*_) >> { throw new ApplicationException(ApplicationException.Code.BACKEND_ERROR, "") }
+        1 * workflowExecutor.startWorkflow(*_) >> { throw new TransientException("") }
     }
 
     def "WorkflowExecutor throws a non-retryable ApplicationException"() {
@@ -101,7 +101,7 @@ class StartWorkflowSpec extends Specification {
         then:
         taskModel.status == FAILED
         taskModel.reasonForIncompletion != null
-        1 * workflowExecutor.startWorkflow(*_) >> { throw new ApplicationException(ApplicationException.Code.NOT_FOUND, "") }
+        1 * workflowExecutor.startWorkflow(*_) >> { throw new NotFoundException("") }
     }
 
     def "WorkflowExecutor throws a RuntimeException"() {
diff --git a/core/src/test/java/com/netflix/conductor/core/events/TestDefaultEventProcessor.java b/core/src/test/java/com/netflix/conductor/core/events/TestDefaultEventProcessor.java
index 8558904023..c37d31d26a 100644
--- a/core/src/test/java/com/netflix/conductor/core/events/TestDefaultEventProcessor.java
+++ b/core/src/test/java/com/netflix/conductor/core/events/TestDefaultEventProcessor.java
@@ -39,7 +39,7 @@
 import com.netflix.conductor.core.config.ConductorProperties;
 import com.netflix.conductor.core.events.queue.Message;
 import com.netflix.conductor.core.events.queue.ObservableQueue;
-import com.netflix.conductor.core.exception.ApplicationException;
+import com.netflix.conductor.core.exception.TransientException;
 import com.netflix.conductor.core.execution.WorkflowExecutor;
 import com.netflix.conductor.core.execution.evaluators.Evaluator;
 import com.netflix.conductor.core.execution.evaluators.JavascriptEvaluator;
@@ -357,9 +357,7 @@ public void testEventProcessorWithRetriableError() {
                 .thenReturn(Collections.singletonList(eventHandler));
         when(executionService.addEventExecution(any())).thenReturn(true);
         when(actionProcessor.execute(any(), any(), any(), any()))
-                .thenThrow(
-                        new ApplicationException(
-                                ApplicationException.Code.BACKEND_ERROR, "some retriable error"));
+                .thenThrow(new TransientException("some retriable error"));
 
         DefaultEventProcessor eventProcessor =
                 new DefaultEventProcessor(
@@ -396,10 +394,7 @@ public void testEventProcessorWithNonRetriableError() {
         when(executionService.addEventExecution(any())).thenReturn(true);
 
         when(actionProcessor.execute(any(), any(), any(), any()))
-                .thenThrow(
-                        new ApplicationException(
-                                ApplicationException.Code.INVALID_INPUT,
-                                "some non-retriable error"));
+                .thenThrow(new IllegalArgumentException("some non-retriable error"));
 
         DefaultEventProcessor eventProcessor =
                 new DefaultEventProcessor(
@@ -458,9 +453,7 @@ public void testExecuteNonRetriableApplicationException() {
                         (Answer<Map<String, Object>>)
                                 invocation -> {
                                     executeInvoked.incrementAndGet();
-                                    throw new ApplicationException(
-                                            ApplicationException.Code.INVALID_INPUT,
-                                            "some non-retriable error");
+                                    throw new IllegalArgumentException("some non-retriable error");
                                 })
                 .when(actionProcessor)
                 .execute(any(), any(), any(), any());
@@ -496,9 +489,7 @@ public void testExecuteRetriableApplicationException() {
                         (Answer<Map<String, Object>>)
                                 invocation -> {
                                     executeInvoked.incrementAndGet();
-                                    throw new ApplicationException(
-                                            ApplicationException.Code.BACKEND_ERROR,
-                                            "some retriable error");
+                                    throw new TransientException("some retriable error");
                                 })
                 .when(actionProcessor)
                 .execute(any(), any(), any(), any());
diff --git a/core/src/test/java/com/netflix/conductor/core/execution/TestWorkflowExecutor.java b/core/src/test/java/com/netflix/conductor/core/execution/TestWorkflowExecutor.java
index 3a9f801e23..ba7ee03762 100644
--- a/core/src/test/java/com/netflix/conductor/core/execution/TestWorkflowExecutor.java
+++ b/core/src/test/java/com/netflix/conductor/core/execution/TestWorkflowExecutor.java
@@ -41,7 +41,8 @@
 import com.netflix.conductor.common.utils.ExternalPayloadStorage;
 import com.netflix.conductor.core.config.ConductorProperties;
 import com.netflix.conductor.core.dal.ExecutionDAOFacade;
-import com.netflix.conductor.core.exception.ApplicationException;
+import com.netflix.conductor.core.exception.ConflictException;
+import com.netflix.conductor.core.exception.NotFoundException;
 import com.netflix.conductor.core.exception.TerminateWorkflowException;
 import com.netflix.conductor.core.execution.evaluators.Evaluator;
 import com.netflix.conductor.core.execution.mapper.*;
@@ -60,7 +61,6 @@
 import com.fasterxml.jackson.databind.ObjectMapper;
 
 import static com.netflix.conductor.common.metadata.tasks.TaskType.*;
-import static com.netflix.conductor.core.exception.ApplicationException.Code.CONFLICT;
 
 import static java.util.Comparator.comparingInt;
 import static java.util.stream.Collectors.groupingBy;
@@ -664,7 +664,7 @@ public void testRestartWorkflow() {
         assertEquals(workflowDef, argumentCaptor.getAllValues().get(1).getWorkflowDefinition());
     }
 
-    @Test(expected = ApplicationException.class)
+    @Test(expected = NotFoundException.class)
     public void testRetryNonTerminalWorkflow() {
         WorkflowModel workflow = new WorkflowModel();
         workflow.setWorkflowId("testRetryNonTerminalWorkflow");
@@ -674,7 +674,7 @@ public void testRetryNonTerminalWorkflow() {
         workflowExecutor.retry(workflow.getWorkflowId(), false);
     }
 
-    @Test(expected = ApplicationException.class)
+    @Test(expected = ConflictException.class)
     public void testRetryWorkflowNoTasks() {
         WorkflowModel workflow = new WorkflowModel();
         workflow.setWorkflowId("ApplicationException");
@@ -685,7 +685,7 @@ public void testRetryWorkflowNoTasks() {
         workflowExecutor.retry(workflow.getWorkflowId(), false);
     }
 
-    @Test(expected = ApplicationException.class)
+    @Test(expected = ConflictException.class)
     public void testRetryWorkflowNoFailedTasks() {
         // setup
         WorkflowModel workflow = new WorkflowModel();
@@ -1243,7 +1243,7 @@ public void testRetryTimedOutWorkflowWithoutFailedTasks() {
         assertEquals(1, updateTasksCalledCounter.get());
     }
 
-    @Test(expected = ApplicationException.class)
+    @Test(expected = ConflictException.class)
     public void testRerunNonTerminalWorkflow() {
         WorkflowModel workflow = new WorkflowModel();
         workflow.setWorkflowId("testRetryNonTerminalWorkflow");
@@ -1805,7 +1805,7 @@ public void testDedupAndAddTasks() {
         assertEquals(3, workflow.getTasks().size());
     }
 
-    @Test(expected = ApplicationException.class)
+    @Test(expected = ConflictException.class)
     public void testTerminateCompletedWorkflow() {
         WorkflowModel workflow = new WorkflowModel();
         workflow.setWorkflowId("testTerminateTerminalWorkflow");
@@ -2008,9 +2008,8 @@ public void testPauseWorkflow() {
         when(executionDAOFacade.getWorkflowModel(workflowId, false)).thenReturn(workflow);
         try {
             workflowExecutor.pauseWorkflow(workflowId);
-            fail("Expected " + ApplicationException.class);
-        } catch (ApplicationException e) {
-            assertEquals(e.getCode(), CONFLICT);
+            fail("Expected " + ConflictException.class);
+        } catch (ConflictException e) {
             verify(executionDAOFacade, never()).updateWorkflow(any(WorkflowModel.class));
             verify(queueDAO, never()).remove(anyString(), anyString());
         }
diff --git a/core/src/test/java/com/netflix/conductor/core/execution/tasks/TestSubWorkflow.java b/core/src/test/java/com/netflix/conductor/core/execution/tasks/TestSubWorkflow.java
index f2dad62f9a..c777a3fb8e 100644
--- a/core/src/test/java/com/netflix/conductor/core/execution/tasks/TestSubWorkflow.java
+++ b/core/src/test/java/com/netflix/conductor/core/execution/tasks/TestSubWorkflow.java
@@ -24,7 +24,8 @@
 
 import com.netflix.conductor.common.config.TestObjectMapperConfiguration;
 import com.netflix.conductor.common.metadata.workflow.WorkflowDef;
-import com.netflix.conductor.core.exception.ApplicationException;
+import com.netflix.conductor.core.exception.NonTransientException;
+import com.netflix.conductor.core.exception.TransientException;
 import com.netflix.conductor.core.execution.WorkflowExecutor;
 import com.netflix.conductor.model.TaskModel;
 import com.netflix.conductor.model.WorkflowModel;
@@ -129,9 +130,7 @@ public void testStartSubWorkflowQueueFailure() {
                         any(),
                         eq(null),
                         any()))
-                .thenThrow(
-                        new ApplicationException(
-                                ApplicationException.Code.BACKEND_ERROR, "QueueDAO failure"));
+                .thenThrow(new TransientException("QueueDAO failure"));
 
         subWorkflow.start(workflowInstance, task, workflowExecutor);
         assertNull("subWorkflowId should be null", task.getSubWorkflowId());
@@ -165,9 +164,7 @@ public void testStartSubWorkflowStartError() {
                         any(),
                         eq(null),
                         any()))
-                .thenThrow(
-                        new ApplicationException(
-                                ApplicationException.Code.INTERNAL_ERROR, failureReason));
+                .thenThrow(new NonTransientException(failureReason));
 
         subWorkflow.start(workflowInstance, task, workflowExecutor);
         assertNull("subWorkflowId should be null", task.getSubWorkflowId());
diff --git a/core/src/test/java/com/netflix/conductor/core/metadata/MetadataMapperServiceTest.java b/core/src/test/java/com/netflix/conductor/core/metadata/MetadataMapperServiceTest.java
index d6d5799a09..55cd1c7d82 100644
--- a/core/src/test/java/com/netflix/conductor/core/metadata/MetadataMapperServiceTest.java
+++ b/core/src/test/java/com/netflix/conductor/core/metadata/MetadataMapperServiceTest.java
@@ -33,7 +33,7 @@
 import com.netflix.conductor.common.metadata.workflow.SubWorkflowParams;
 import com.netflix.conductor.common.metadata.workflow.WorkflowDef;
 import com.netflix.conductor.common.metadata.workflow.WorkflowTask;
-import com.netflix.conductor.core.exception.ApplicationException;
+import com.netflix.conductor.core.exception.NotFoundException;
 import com.netflix.conductor.core.exception.TerminateWorkflowException;
 import com.netflix.conductor.dao.MetadataDAO;
 
@@ -160,12 +160,8 @@ public void testMetadataPopulationMissingDefinitions() {
 
         try {
             metadataMapperService.populateTaskDefinitions(workflowDefinition);
-        } catch (ApplicationException ae) {
-            if (ae.getCode() == ApplicationException.Code.INVALID_INPUT) {
-                fail("Missing task definitions are not set to a default TaskDef");
-            } else {
-                throw ae;
-            }
+        } catch (NotFoundException nfe) {
+            fail("Missing TaskDefinitions are not defaulted");
         }
     }
 
diff --git a/core/src/test/java/com/netflix/conductor/dao/ExecutionDAOTest.java b/core/src/test/java/com/netflix/conductor/dao/ExecutionDAOTest.java
index 5133bfa0bc..f996adc0fe 100644
--- a/core/src/test/java/com/netflix/conductor/dao/ExecutionDAOTest.java
+++ b/core/src/test/java/com/netflix/conductor/dao/ExecutionDAOTest.java
@@ -30,7 +30,6 @@
 import com.netflix.conductor.common.metadata.tasks.TaskDef;
 import com.netflix.conductor.common.metadata.workflow.WorkflowDef;
 import com.netflix.conductor.common.metadata.workflow.WorkflowTask;
-import com.netflix.conductor.core.exception.ApplicationException;
 import com.netflix.conductor.model.TaskModel;
 import com.netflix.conductor.model.WorkflowModel;
 
@@ -89,14 +88,14 @@ public void testCreateTaskException() {
         task.setTaskId(UUID.randomUUID().toString());
         task.setTaskDefName("task1");
 
-        expectedException.expect(ApplicationException.class);
+        expectedException.expect(IllegalArgumentException.class);
         expectedException.expectMessage("Workflow instance id cannot be null");
-        getExecutionDAO().createTasks(Collections.singletonList(task));
+        getExecutionDAO().createTasks(List.of(task));
 
         task.setWorkflowInstanceId(UUID.randomUUID().toString());
-        expectedException.expect(ApplicationException.class);
+        expectedException.expect(IllegalArgumentException.class);
         expectedException.expectMessage("Task reference name cannot be null");
-        getExecutionDAO().createTasks(Collections.singletonList(task));
+        getExecutionDAO().createTasks(List.of(task));
     }
 
     @Test
@@ -108,7 +107,7 @@ public void testCreateTaskException2() {
         task.setTaskDefName("task1");
         task.setWorkflowInstanceId(UUID.randomUUID().toString());
 
-        expectedException.expect(ApplicationException.class);
+        expectedException.expect(IllegalArgumentException.class);
         expectedException.expectMessage("Task reference name cannot be null");
         getExecutionDAO().createTasks(Collections.singletonList(task));
     }
diff --git a/core/src/test/java/com/netflix/conductor/service/MetadataServiceTest.java b/core/src/test/java/com/netflix/conductor/service/MetadataServiceTest.java
index bc508a7b07..f1985e2716 100644
--- a/core/src/test/java/com/netflix/conductor/service/MetadataServiceTest.java
+++ b/core/src/test/java/com/netflix/conductor/service/MetadataServiceTest.java
@@ -32,7 +32,7 @@
 import com.netflix.conductor.common.metadata.workflow.WorkflowDef;
 import com.netflix.conductor.common.metadata.workflow.WorkflowTask;
 import com.netflix.conductor.core.config.ConductorProperties;
-import com.netflix.conductor.core.exception.ApplicationException;
+import com.netflix.conductor.core.exception.NotFoundException;
 import com.netflix.conductor.dao.EventHandlerDAO;
 import com.netflix.conductor.dao.MetadataDAO;
 
@@ -154,7 +154,7 @@ public void testUpdateTaskDefNull() {
         fail("metadataService.updateTaskDef did not throw ConstraintViolationException !");
     }
 
-    @Test(expected = ApplicationException.class)
+    @Test(expected = NotFoundException.class)
     public void testUpdateTaskDefNotExisting() {
         TaskDef taskDef = new TaskDef();
         taskDef.setName("test");
@@ -163,7 +163,7 @@ public void testUpdateTaskDefNotExisting() {
         metadataService.updateTaskDef(taskDef);
     }
 
-    @Test(expected = ApplicationException.class)
+    @Test(expected = NotFoundException.class)
     public void testUpdateTaskDefDaoException() {
         TaskDef taskDef = new TaskDef();
         taskDef.setName("test");
diff --git a/core/src/test/java/com/netflix/conductor/service/WorkflowServiceTest.java b/core/src/test/java/com/netflix/conductor/service/WorkflowServiceTest.java
index b710e0e200..aef6e5a2eb 100644
--- a/core/src/test/java/com/netflix/conductor/service/WorkflowServiceTest.java
+++ b/core/src/test/java/com/netflix/conductor/service/WorkflowServiceTest.java
@@ -35,7 +35,7 @@
 import com.netflix.conductor.common.run.SearchResult;
 import com.netflix.conductor.common.run.Workflow;
 import com.netflix.conductor.common.run.WorkflowSummary;
-import com.netflix.conductor.core.exception.ApplicationException;
+import com.netflix.conductor.core.exception.NotFoundException;
 import com.netflix.conductor.core.execution.WorkflowExecutor;
 
 import static com.netflix.conductor.TestUtils.getConstraintViolationMessages;
@@ -165,21 +165,11 @@ public void testStartWorkflowParam() {
         assertEquals("w112", workflowService.startWorkflow("test", 1, "c123", input));
     }
 
-    @Test(expected = ApplicationException.class)
-    public void testApplicationExceptionStartWorkflowMessageParam() {
-        try {
-            when(metadataService.getWorkflowDef("test", 1)).thenReturn(null);
+    @Test(expected = NotFoundException.class)
+    public void testNotFoundExceptionStartWorkflowMessageParam() {
+        when(metadataService.getWorkflowDef("test", 1)).thenReturn(null);
 
-            Map<String, Object> input = new HashMap<>();
-            input.put("1", "abc");
-
-            workflowService.startWorkflow("test", 1, "c123", input);
-        } catch (ApplicationException ex) {
-            String message = "No such workflow found by name: test, version: 1";
-            assertEquals(message, ex.getMessage());
-            throw ex;
-        }
-        fail("ApplicationException did not throw!");
+        workflowService.startWorkflow("test", 1, "c123", Map.of("1", "abc"));
     }
 
     @Test(expected = ConstraintViolationException.class)
@@ -247,17 +237,10 @@ public void testGetExecutionStatusNoWorkflowId() {
         }
     }
 
-    @Test(expected = ApplicationException.class)
-    public void testApplicationExceptionGetExecutionStatus() {
-        try {
-            when(executionService.getExecutionStatus(anyString(), anyBoolean())).thenReturn(null);
-            workflowService.getExecutionStatus("w123", true);
-        } catch (ApplicationException ex) {
-            String message = "Workflow with Id: w123 not found.";
-            assertEquals(message, ex.getMessage());
-            throw ex;
-        }
-        fail("ApplicationException did not throw!");
+    @Test(expected = NotFoundException.class)
+    public void testNotFoundExceptionGetExecutionStatus() {
+        when(executionService.getExecutionStatus(anyString(), anyBoolean())).thenReturn(null);
+        workflowService.getExecutionStatus("w123", true);
     }
 
     @Test
diff --git a/es6-persistence/src/main/java/com/netflix/conductor/es6/dao/index/ElasticSearchDAOV6.java b/es6-persistence/src/main/java/com/netflix/conductor/es6/dao/index/ElasticSearchDAOV6.java
index 0d40fd61ad..716be69815 100644
--- a/es6-persistence/src/main/java/com/netflix/conductor/es6/dao/index/ElasticSearchDAOV6.java
+++ b/es6-persistence/src/main/java/com/netflix/conductor/es6/dao/index/ElasticSearchDAOV6.java
@@ -63,7 +63,7 @@
 import com.netflix.conductor.common.run.TaskSummary;
 import com.netflix.conductor.common.run.WorkflowSummary;
 import com.netflix.conductor.core.events.queue.Message;
-import com.netflix.conductor.core.exception.ApplicationException;
+import com.netflix.conductor.core.exception.TransientException;
 import com.netflix.conductor.dao.IndexDAO;
 import com.netflix.conductor.es6.config.ElasticSearchProperties;
 import com.netflix.conductor.es6.dao.query.parser.internal.ParserException;
@@ -701,9 +701,7 @@ public CompletableFuture<Void> asyncRemoveWorkflow(String workflowId) {
     @Override
     public void updateWorkflow(String workflowInstanceId, String[] keys, Object[] values) {
         if (keys.length != values.length) {
-            throw new ApplicationException(
-                    ApplicationException.Code.INVALID_INPUT,
-                    "Number of keys and values do not match");
+            throw new IllegalArgumentException("Number of keys and values do not match");
         }
 
         long startTime = Instant.now().toEpochMilli();
@@ -774,8 +772,7 @@ private long count(String structuredQuery, String freeTextQuery, String docType)
             SearchResponse response = srb.get();
             return response.getHits().getTotalHits();
         } catch (ParserException e) {
-            throw new ApplicationException(
-                    ApplicationException.Code.BACKEND_ERROR, e.getMessage(), e);
+            throw new TransientException(e.getMessage(), e);
         }
     }
 
@@ -802,8 +799,7 @@ private SearchResult<String> search(
 
             return mapSearchResult(srb.get());
         } catch (ParserException e) {
-            throw new ApplicationException(
-                    ApplicationException.Code.BACKEND_ERROR, e.getMessage(), e);
+            throw new TransientException(e.getMessage(), e);
         }
     }
 
diff --git a/es6-persistence/src/main/java/com/netflix/conductor/es6/dao/index/ElasticSearchRestDAOV6.java b/es6-persistence/src/main/java/com/netflix/conductor/es6/dao/index/ElasticSearchRestDAOV6.java
index a55d2f7d3f..764329ab35 100644
--- a/es6-persistence/src/main/java/com/netflix/conductor/es6/dao/index/ElasticSearchRestDAOV6.java
+++ b/es6-persistence/src/main/java/com/netflix/conductor/es6/dao/index/ElasticSearchRestDAOV6.java
@@ -65,7 +65,8 @@
 import com.netflix.conductor.common.run.TaskSummary;
 import com.netflix.conductor.common.run.WorkflowSummary;
 import com.netflix.conductor.core.events.queue.Message;
-import com.netflix.conductor.core.exception.ApplicationException;
+import com.netflix.conductor.core.exception.NonTransientException;
+import com.netflix.conductor.core.exception.TransientException;
 import com.netflix.conductor.dao.IndexDAO;
 import com.netflix.conductor.es6.config.ElasticSearchProperties;
 import com.netflix.conductor.es6.dao.query.parser.internal.ParserException;
@@ -291,7 +292,7 @@ private String updateIndexName(String type) {
             return indexName;
         } catch (IOException e) {
             LOGGER.error("Failed to update log index name: {}", indexName, e);
-            throw new ApplicationException(e.getMessage(), e);
+            throw new NonTransientException("Failed to update log index name: " + indexName, e);
         }
     }
 
@@ -725,8 +726,7 @@ public SearchResult<String> searchWorkflows(
             return searchObjectIdsViaExpression(
                     query, start, count, sort, freeText, WORKFLOW_DOC_TYPE);
         } catch (Exception e) {
-            throw new ApplicationException(
-                    ApplicationException.Code.BACKEND_ERROR, e.getMessage(), e);
+            throw new TransientException(e.getMessage(), e);
         }
     }
 
@@ -736,8 +736,7 @@ public SearchResult<String> searchTasks(
         try {
             return searchObjectIdsViaExpression(query, start, count, sort, freeText, TASK_DOC_TYPE);
         } catch (Exception e) {
-            throw new ApplicationException(
-                    ApplicationException.Code.BACKEND_ERROR, e.getMessage(), e);
+            throw new TransientException(e.getMessage(), e);
         }
     }
 
@@ -774,9 +773,7 @@ public CompletableFuture<Void> asyncRemoveWorkflow(String workflowId) {
     public void updateWorkflow(String workflowInstanceId, String[] keys, Object[] values) {
         try {
             if (keys.length != values.length) {
-                throw new ApplicationException(
-                        ApplicationException.Code.INVALID_INPUT,
-                        "Number of keys and values do not match");
+                throw new IllegalArgumentException("Number of keys and values do not match");
             }
 
             long startTime = Instant.now().toEpochMilli();
@@ -954,8 +951,7 @@ public long getWorkflowCount(String query, String freeText) {
         try {
             return getObjectCounts(query, freeText, WORKFLOW_DOC_TYPE);
         } catch (Exception e) {
-            throw new ApplicationException(
-                    ApplicationException.Code.BACKEND_ERROR, e.getMessage(), e);
+            throw new TransientException(e.getMessage(), e);
         }
     }
 
diff --git a/grpc-server/src/main/java/com/netflix/conductor/grpc/server/service/MetadataServiceImpl.java b/grpc-server/src/main/java/com/netflix/conductor/grpc/server/service/MetadataServiceImpl.java
index 32aaeb0bb8..72ed91331a 100644
--- a/grpc-server/src/main/java/com/netflix/conductor/grpc/server/service/MetadataServiceImpl.java
+++ b/grpc-server/src/main/java/com/netflix/conductor/grpc/server/service/MetadataServiceImpl.java
@@ -21,7 +21,7 @@
 
 import com.netflix.conductor.common.metadata.tasks.TaskDef;
 import com.netflix.conductor.common.metadata.workflow.WorkflowDef;
-import com.netflix.conductor.core.exception.ApplicationException;
+import com.netflix.conductor.core.exception.NotFoundException;
 import com.netflix.conductor.grpc.MetadataServiceGrpc;
 import com.netflix.conductor.grpc.MetadataServicePb;
 import com.netflix.conductor.grpc.ProtoMapper;
@@ -82,7 +82,7 @@ public void getWorkflow(
                             .setWorkflow(workflow)
                             .build());
             response.onCompleted();
-        } catch (ApplicationException e) {
+        } catch (NotFoundException e) {
             // TODO replace this with gRPC exception interceptor.
             response.onError(
                     Status.NOT_FOUND
diff --git a/grpc-server/src/main/java/com/netflix/conductor/grpc/server/service/WorkflowServiceImpl.java b/grpc-server/src/main/java/com/netflix/conductor/grpc/server/service/WorkflowServiceImpl.java
index 42493c552b..3b10b33106 100644
--- a/grpc-server/src/main/java/com/netflix/conductor/grpc/server/service/WorkflowServiceImpl.java
+++ b/grpc-server/src/main/java/com/netflix/conductor/grpc/server/service/WorkflowServiceImpl.java
@@ -26,8 +26,7 @@
 import com.netflix.conductor.common.run.SearchResult;
 import com.netflix.conductor.common.run.Workflow;
 import com.netflix.conductor.common.run.WorkflowSummary;
-import com.netflix.conductor.core.exception.ApplicationException;
-import com.netflix.conductor.core.exception.ApplicationException.Code;
+import com.netflix.conductor.core.exception.NotFoundException;
 import com.netflix.conductor.grpc.ProtoMapper;
 import com.netflix.conductor.grpc.SearchPb;
 import com.netflix.conductor.grpc.WorkflowServiceGrpc;
@@ -79,16 +78,14 @@ public void startWorkflow(
             response.onNext(
                     WorkflowServicePb.StartWorkflowResponse.newBuilder().setWorkflowId(id).build());
             response.onCompleted();
-        } catch (ApplicationException ae) {
-            if (ae.getCode() == Code.NOT_FOUND) {
-                response.onError(
-                        Status.NOT_FOUND
-                                .withDescription(
-                                        "No such workflow found by name=" + request.getName())
-                                .asRuntimeException());
-            } else {
-                GRPC_HELPER.onError(response, ae);
-            }
+        } catch (NotFoundException nfe) {
+            response.onError(
+                    Status.NOT_FOUND
+                            .withDescription("No such workflow found by name=" + request.getName())
+                            .asRuntimeException());
+        } catch (Exception e) {
+
+            GRPC_HELPER.onError(response, e);
         }
     }
 
diff --git a/redis-concurrency-limit/src/main/java/com/netflix/conductor/redis/limit/RedisConcurrentExecutionLimitDAO.java b/redis-concurrency-limit/src/main/java/com/netflix/conductor/redis/limit/RedisConcurrentExecutionLimitDAO.java
index 4107997252..ceb7fec101 100644
--- a/redis-concurrency-limit/src/main/java/com/netflix/conductor/redis/limit/RedisConcurrentExecutionLimitDAO.java
+++ b/redis-concurrency-limit/src/main/java/com/netflix/conductor/redis/limit/RedisConcurrentExecutionLimitDAO.java
@@ -24,7 +24,7 @@
 
 import com.netflix.conductor.annotations.Trace;
 import com.netflix.conductor.common.metadata.tasks.TaskDef;
-import com.netflix.conductor.core.exception.ApplicationException;
+import com.netflix.conductor.core.exception.TransientException;
 import com.netflix.conductor.dao.ConcurrentExecutionLimitDAO;
 import com.netflix.conductor.metrics.Monitors;
 import com.netflix.conductor.model.TaskModel;
@@ -75,7 +75,7 @@ public void addTaskToLimit(TaskModel task) {
                             "Error updating taskDefLimit for task - %s:%s in workflow: %s",
                             task.getTaskDefName(), task.getTaskId(), task.getWorkflowInstanceId());
             LOGGER.error(errorMsg, e);
-            throw new ApplicationException(ApplicationException.Code.BACKEND_ERROR, errorMsg, e);
+            throw new TransientException(errorMsg, e);
         }
     }
 
@@ -104,7 +104,7 @@ public void removeTaskFromLimit(TaskModel task) {
                             "Error updating taskDefLimit for task - %s:%s in workflow: %s",
                             task.getTaskDefName(), task.getTaskId(), task.getWorkflowInstanceId());
             LOGGER.error(errorMsg, e);
-            throw new ApplicationException(ApplicationException.Code.BACKEND_ERROR, errorMsg, e);
+            throw new TransientException(errorMsg, e);
         }
     }
 
@@ -156,7 +156,7 @@ public boolean exceedsLimit(TaskModel task) {
                             "Failed to get in progress limit - %s:%s in workflow :%s",
                             task.getTaskDefName(), task.getTaskId(), task.getWorkflowInstanceId());
             LOGGER.error(errorMsg, e);
-            throw new ApplicationException(ApplicationException.Code.BACKEND_ERROR, errorMsg);
+            throw new TransientException(errorMsg);
         }
     }
 
diff --git a/redis-persistence/src/main/java/com/netflix/conductor/redis/dao/RedisEventHandlerDAO.java b/redis-persistence/src/main/java/com/netflix/conductor/redis/dao/RedisEventHandlerDAO.java
index 263e4ec77f..1742786e69 100644
--- a/redis-persistence/src/main/java/com/netflix/conductor/redis/dao/RedisEventHandlerDAO.java
+++ b/redis-persistence/src/main/java/com/netflix/conductor/redis/dao/RedisEventHandlerDAO.java
@@ -24,8 +24,8 @@
 
 import com.netflix.conductor.common.metadata.events.EventHandler;
 import com.netflix.conductor.core.config.ConductorProperties;
-import com.netflix.conductor.core.exception.ApplicationException;
-import com.netflix.conductor.core.exception.ApplicationException.Code;
+import com.netflix.conductor.core.exception.ConflictException;
+import com.netflix.conductor.core.exception.NotFoundException;
 import com.netflix.conductor.dao.EventHandlerDAO;
 import com.netflix.conductor.redis.config.AnyRedisCondition;
 import com.netflix.conductor.redis.config.RedisProperties;
@@ -55,9 +55,8 @@ public RedisEventHandlerDAO(
     public void addEventHandler(EventHandler eventHandler) {
         Preconditions.checkNotNull(eventHandler.getName(), "Missing Name");
         if (getEventHandler(eventHandler.getName()) != null) {
-            throw new ApplicationException(
-                    Code.CONFLICT,
-                    "EventHandler with name " + eventHandler.getName() + " already exists!");
+            throw new ConflictException(
+                    "EventHandler with name %s already exists!", eventHandler.getName());
         }
         index(eventHandler);
         jedisProxy.hset(nsKey(EVENT_HANDLERS), eventHandler.getName(), toJson(eventHandler));
@@ -69,9 +68,8 @@ public void updateEventHandler(EventHandler eventHandler) {
         Preconditions.checkNotNull(eventHandler.getName(), "Missing Name");
         EventHandler existing = getEventHandler(eventHandler.getName());
         if (existing == null) {
-            throw new ApplicationException(
-                    Code.NOT_FOUND,
-                    "EventHandler with name " + eventHandler.getName() + " not found!");
+            throw new NotFoundException(
+                    "EventHandler with name %s not found!", eventHandler.getName());
         }
         index(eventHandler);
         jedisProxy.hset(nsKey(EVENT_HANDLERS), eventHandler.getName(), toJson(eventHandler));
@@ -82,8 +80,7 @@ public void updateEventHandler(EventHandler eventHandler) {
     public void removeEventHandler(String name) {
         EventHandler existing = getEventHandler(name);
         if (existing == null) {
-            throw new ApplicationException(
-                    Code.NOT_FOUND, "EventHandler with name " + name + " not found!");
+            throw new NotFoundException("EventHandler with name %s not found!", name);
         }
         jedisProxy.hdel(nsKey(EVENT_HANDLERS), name);
         recordRedisDaoRequests("removeEventHandler");
@@ -128,11 +125,9 @@ public List<EventHandler> getEventHandlersForEvent(String event, boolean activeO
                         && (!activeOnly || eventHandler.isActive())) {
                     handlers.add(eventHandler);
                 }
-            } catch (ApplicationException ae) {
-                if (ae.getCode() == Code.NOT_FOUND) {
-                    LOGGER.info("No matching event handler found for event: {}", event);
-                }
-                throw ae;
+            } catch (NotFoundException nfe) {
+                LOGGER.info("No matching event handler found for event: {}", event);
+                throw nfe;
             }
         }
         return handlers;
diff --git a/redis-persistence/src/main/java/com/netflix/conductor/redis/dao/RedisExecutionDAO.java b/redis-persistence/src/main/java/com/netflix/conductor/redis/dao/RedisExecutionDAO.java
index e653d3d6f5..33902640d4 100644
--- a/redis-persistence/src/main/java/com/netflix/conductor/redis/dao/RedisExecutionDAO.java
+++ b/redis-persistence/src/main/java/com/netflix/conductor/redis/dao/RedisExecutionDAO.java
@@ -24,8 +24,7 @@
 import com.netflix.conductor.common.metadata.events.EventExecution;
 import com.netflix.conductor.common.metadata.tasks.TaskDef;
 import com.netflix.conductor.core.config.ConductorProperties;
-import com.netflix.conductor.core.exception.ApplicationException;
-import com.netflix.conductor.core.exception.ApplicationException.Code;
+import com.netflix.conductor.core.exception.TransientException;
 import com.netflix.conductor.dao.ConcurrentExecutionLimitDAO;
 import com.netflix.conductor.dao.ExecutionDAO;
 import com.netflix.conductor.metrics.Monitors;
@@ -682,10 +681,8 @@ public boolean addEventExecution(EventExecution eventExecution) {
 
             return added;
         } catch (Exception e) {
-            throw new ApplicationException(
-                    Code.BACKEND_ERROR,
-                    "Unable to add event execution for " + eventExecution.getId(),
-                    e);
+            throw new TransientException(
+                    "Unable to add event execution for " + eventExecution.getId(), e);
         }
     }
 
@@ -706,10 +703,8 @@ public void updateEventExecution(EventExecution eventExecution) {
             recordRedisDaoPayloadSize(
                     "updateEventExecution", json.length(), eventExecution.getEvent(), "n/a");
         } catch (Exception e) {
-            throw new ApplicationException(
-                    Code.BACKEND_ERROR,
-                    "Unable to update event execution for " + eventExecution.getId(),
-                    e);
+            throw new TransientException(
+                    "Unable to update event execution for " + eventExecution.getId(), e);
         }
     }
 
@@ -726,10 +721,8 @@ public void removeEventExecution(EventExecution eventExecution) {
             jedisProxy.hdel(key, eventExecution.getId());
             recordRedisDaoEventRequests("removeEventExecution", eventExecution.getEvent());
         } catch (Exception e) {
-            throw new ApplicationException(
-                    Code.BACKEND_ERROR,
-                    "Unable to remove event execution for " + eventExecution.getId(),
-                    e);
+            throw new TransientException(
+                    "Unable to remove event execution for " + eventExecution.getId(), e);
         }
     }
 
@@ -754,10 +747,8 @@ public List<EventExecution> getEventExecutions(
             return executions;
 
         } catch (Exception e) {
-            throw new ApplicationException(
-                    Code.BACKEND_ERROR,
-                    "Unable to get event executions for " + eventHandlerName,
-                    e);
+            throw new TransientException(
+                    "Unable to get event executions for " + eventHandlerName, e);
         }
     }
 
@@ -770,7 +761,7 @@ private void validate(TaskModel task) {
             Preconditions.checkNotNull(
                     task.getReferenceTaskName(), "Task reference name cannot be null");
         } catch (NullPointerException npe) {
-            throw new ApplicationException(Code.INVALID_INPUT, npe.getMessage(), npe);
+            throw new IllegalArgumentException(npe.getMessage(), npe);
         }
     }
 }
diff --git a/redis-persistence/src/main/java/com/netflix/conductor/redis/dao/RedisMetadataDAO.java b/redis-persistence/src/main/java/com/netflix/conductor/redis/dao/RedisMetadataDAO.java
index 81d671b481..fedb1895bd 100644
--- a/redis-persistence/src/main/java/com/netflix/conductor/redis/dao/RedisMetadataDAO.java
+++ b/redis-persistence/src/main/java/com/netflix/conductor/redis/dao/RedisMetadataDAO.java
@@ -32,8 +32,8 @@
 import com.netflix.conductor.common.metadata.tasks.TaskDef;
 import com.netflix.conductor.common.metadata.workflow.WorkflowDef;
 import com.netflix.conductor.core.config.ConductorProperties;
-import com.netflix.conductor.core.exception.ApplicationException;
-import com.netflix.conductor.core.exception.ApplicationException.Code;
+import com.netflix.conductor.core.exception.ConflictException;
+import com.netflix.conductor.core.exception.NotFoundException;
 import com.netflix.conductor.dao.MetadataDAO;
 import com.netflix.conductor.metrics.Monitors;
 import com.netflix.conductor.redis.config.AnyRedisCondition;
@@ -149,8 +149,7 @@ public void removeTaskDef(String name) {
         Preconditions.checkNotNull(name, "TaskDef name cannot be null");
         Long result = jedisProxy.hdel(nsKey(ALL_TASK_DEFS), name);
         if (!result.equals(1L)) {
-            throw new ApplicationException(
-                    Code.NOT_FOUND, "Cannot remove the task - no such task definition");
+            throw new NotFoundException("Cannot remove the task - no such task definition");
         }
         recordRedisDaoRequests("removeTaskDef");
         refreshTaskDefs();
@@ -160,8 +159,7 @@ public void removeTaskDef(String name) {
     public void createWorkflowDef(WorkflowDef def) {
         if (jedisProxy.hexists(
                 nsKey(WORKFLOW_DEF, def.getName()), String.valueOf(def.getVersion()))) {
-            throw new ApplicationException(
-                    Code.CONFLICT, "Workflow with " + def.key() + " already exists!");
+            throw new ConflictException("Workflow with %s already exists!", def.key());
         }
         _createOrUpdate(def);
     }
@@ -244,12 +242,9 @@ public void removeWorkflowDef(String name, Integer version) {
         Preconditions.checkNotNull(version, "Input version cannot be null");
         Long result = jedisProxy.hdel(nsKey(WORKFLOW_DEF, name), String.valueOf(version));
         if (!result.equals(1L)) {
-            throw new ApplicationException(
-                    Code.NOT_FOUND,
-                    String.format(
-                            "Cannot remove the workflow - no such workflow"
-                                    + " definition: %s version: %d",
-                            name, version));
+            throw new NotFoundException(
+                    "Cannot remove the workflow - no such workflow" + " definition: %s version: %d",
+                    name, version);
         }
 
         // check if there are any more versions remaining if not delete the
@@ -257,7 +252,7 @@ public void removeWorkflowDef(String name, Integer version) {
         Optional<Integer> optionMaxVersion = getWorkflowMaxVersion(name);
 
         // delete workflow name
-        if (!optionMaxVersion.isPresent()) {
+        if (optionMaxVersion.isEmpty()) {
             jedisProxy.srem(nsKey(WORKFLOW_DEF_NAMES), name);
         }
 
diff --git a/redis-persistence/src/test/java/com/netflix/conductor/redis/dao/RedisMetadataDAOTest.java b/redis-persistence/src/test/java/com/netflix/conductor/redis/dao/RedisMetadataDAOTest.java
index 9a303ce529..bb581cf207 100644
--- a/redis-persistence/src/test/java/com/netflix/conductor/redis/dao/RedisMetadataDAOTest.java
+++ b/redis-persistence/src/test/java/com/netflix/conductor/redis/dao/RedisMetadataDAOTest.java
@@ -33,7 +33,8 @@
 import com.netflix.conductor.common.metadata.tasks.TaskDef.TimeoutPolicy;
 import com.netflix.conductor.common.metadata.workflow.WorkflowDef;
 import com.netflix.conductor.core.config.ConductorProperties;
-import com.netflix.conductor.core.exception.ApplicationException;
+import com.netflix.conductor.core.exception.ConflictException;
+import com.netflix.conductor.core.exception.NotFoundException;
 import com.netflix.conductor.redis.config.RedisProperties;
 import com.netflix.conductor.redis.jedis.JedisMock;
 import com.netflix.conductor.redis.jedis.JedisProxy;
@@ -67,7 +68,7 @@ public void init() {
                 new RedisMetadataDAO(jedisProxy, objectMapper, conductorProperties, properties);
     }
 
-    @Test(expected = ApplicationException.class)
+    @Test(expected = ConflictException.class)
     public void testDup() {
         WorkflowDef def = new WorkflowDef();
         def.setName("testDup");
@@ -159,7 +160,7 @@ public void testWorkflowDefOperations() {
         assertEquals(workflow.getVersion(), 3);
     }
 
-    @Test(expected = ApplicationException.class)
+    @Test(expected = NotFoundException.class)
     public void removeInvalidWorkflowDef() {
         redisMetadataDAO.removeWorkflowDef("hello", 1);
     }
@@ -220,8 +221,8 @@ public void testTaskDefOperations() {
         assertEquals(def.getName(), all.get(0).getName());
     }
 
-    @Test(expected = ApplicationException.class)
+    @Test(expected = NotFoundException.class)
     public void testRemoveTaskDef() {
-        redisMetadataDAO.removeTaskDef("test" + UUID.randomUUID().toString());
+        redisMetadataDAO.removeTaskDef("test" + UUID.randomUUID());
     }
 }
diff --git a/rest/src/main/java/com/netflix/conductor/rest/controllers/ApplicationExceptionMapper.java b/rest/src/main/java/com/netflix/conductor/rest/controllers/ApplicationExceptionMapper.java
index 32eb2e212d..ab5c47eee9 100644
--- a/rest/src/main/java/com/netflix/conductor/rest/controllers/ApplicationExceptionMapper.java
+++ b/rest/src/main/java/com/netflix/conductor/rest/controllers/ApplicationExceptionMapper.java
@@ -12,6 +12,9 @@
  */
 package com.netflix.conductor.rest.controllers;
 
+import java.util.HashMap;
+import java.util.Map;
+
 import javax.servlet.http.HttpServletRequest;
 
 import org.slf4j.Logger;
@@ -23,15 +26,14 @@
 import org.springframework.web.bind.annotation.RestControllerAdvice;
 
 import com.netflix.conductor.common.validation.ErrorResponse;
-import com.netflix.conductor.core.exception.ApplicationException;
+import com.netflix.conductor.core.exception.ConflictException;
+import com.netflix.conductor.core.exception.NotFoundException;
+import com.netflix.conductor.core.exception.TransientException;
 import com.netflix.conductor.core.utils.Utils;
 import com.netflix.conductor.metrics.Monitors;
 
 import com.fasterxml.jackson.databind.exc.InvalidFormatException;
 
-import static com.netflix.conductor.core.exception.ApplicationException.Code.INTERNAL_ERROR;
-import static com.netflix.conductor.core.exception.ApplicationException.Code.INVALID_INPUT;
-
 @RestControllerAdvice
 @Order(ValidationExceptionMapper.ORDER + 1)
 public class ApplicationExceptionMapper {
@@ -40,45 +42,40 @@ public class ApplicationExceptionMapper {
 
     private final String host = Utils.getServerId();
 
-    @ExceptionHandler(ApplicationException.class)
-    public ResponseEntity<ErrorResponse> handleApplicationException(
-            HttpServletRequest request, ApplicationException ex) {
-        logException(request, ex);
-
-        Monitors.error("error", String.valueOf(ex.getHttpStatusCode()));
+    private static final Map<Class<? extends Throwable>, HttpStatus> EXCEPTION_STATUS_MAP =
+            new HashMap<>();
 
-        return new ResponseEntity<>(
-                toErrorResponse(ex), HttpStatus.valueOf(ex.getHttpStatusCode()));
+    static {
+        EXCEPTION_STATUS_MAP.put(NotFoundException.class, HttpStatus.NOT_FOUND);
+        EXCEPTION_STATUS_MAP.put(ConflictException.class, HttpStatus.CONFLICT);
+        EXCEPTION_STATUS_MAP.put(IllegalArgumentException.class, HttpStatus.BAD_REQUEST);
+        EXCEPTION_STATUS_MAP.put(InvalidFormatException.class, HttpStatus.INTERNAL_SERVER_ERROR);
     }
 
     @ExceptionHandler(Throwable.class)
     public ResponseEntity<ErrorResponse> handleAll(HttpServletRequest request, Throwable th) {
         logException(request, th);
 
-        ApplicationException.Code code =
-                (th instanceof IllegalArgumentException || th instanceof InvalidFormatException)
-                        ? INVALID_INPUT
-                        : INTERNAL_ERROR;
+        HttpStatus status =
+                EXCEPTION_STATUS_MAP.getOrDefault(th.getClass(), HttpStatus.INTERNAL_SERVER_ERROR);
+
+        ErrorResponse errorResponse = new ErrorResponse();
+        errorResponse.setInstance(host);
+        errorResponse.setStatus(status.value());
+        errorResponse.setMessage(th.getMessage());
+        errorResponse.setRetryable(
+                th instanceof TransientException); // set it to true for TransientException
 
-        ApplicationException ex = new ApplicationException(code, th.getMessage(), th);
+        Monitors.error("error", String.valueOf(status.value()));
 
-        return handleApplicationException(request, ex);
+        return new ResponseEntity<>(errorResponse, status);
     }
 
     private void logException(HttpServletRequest request, Throwable exception) {
         LOGGER.error(
-                String.format(
-                        "Error %s url: '%s'",
-                        exception.getClass().getSimpleName(), request.getRequestURI()),
+                "Error {} url: '{}'",
+                exception.getClass().getSimpleName(),
+                request.getRequestURI(),
                 exception);
     }
-
-    private ErrorResponse toErrorResponse(ApplicationException ex) {
-        ErrorResponse errorResponse = new ErrorResponse();
-        errorResponse.setInstance(host);
-        errorResponse.setStatus(ex.getHttpStatusCode());
-        errorResponse.setMessage(ex.getMessage());
-        errorResponse.setRetryable(ex.isRetryable());
-        return errorResponse;
-    }
 }
diff --git a/test-harness/src/test/groovy/com/netflix/conductor/test/integration/SimpleWorkflowSpec.groovy b/test-harness/src/test/groovy/com/netflix/conductor/test/integration/SimpleWorkflowSpec.groovy
index 276514742c..7dbdc54c5a 100644
--- a/test-harness/src/test/groovy/com/netflix/conductor/test/integration/SimpleWorkflowSpec.groovy
+++ b/test-harness/src/test/groovy/com/netflix/conductor/test/integration/SimpleWorkflowSpec.groovy
@@ -22,13 +22,13 @@ import com.netflix.conductor.common.metadata.tasks.TaskType
 import com.netflix.conductor.common.metadata.workflow.WorkflowDef
 import com.netflix.conductor.common.metadata.workflow.WorkflowTask
 import com.netflix.conductor.common.run.Workflow
-import com.netflix.conductor.core.exception.ApplicationException
+import com.netflix.conductor.core.exception.ConflictException
+import com.netflix.conductor.core.exception.NotFoundException
 import com.netflix.conductor.dao.QueueDAO
 import com.netflix.conductor.test.base.AbstractSpecification
 
 import spock.lang.Shared
 
-import static com.netflix.conductor.core.exception.ApplicationException.Code.CONFLICT
 import static com.netflix.conductor.test.util.WorkflowTestUtil.verifyPolledAndAcknowledgedTask
 
 class SimpleWorkflowSpec extends AbstractSpecification {
@@ -188,8 +188,8 @@ class SimpleWorkflowSpec extends AbstractSpecification {
         workflowExecutor.restart(workflowInstanceId, false)
 
         then: "Ensure that a exception is thrown when a running workflow is being rewind"
-        def exceptionThrown = thrown(ApplicationException)
-        exceptionThrown.code == CONFLICT
+        def exceptionThrown = thrown(ConflictException.class)
+        exceptionThrown != null
 
         when: "'integration_task_1' is polled and failed with terminal error"
         def polledIntegrationTask1 = workflowExecutionService.poll('integration_task_1', 'task1.integration.worker')
@@ -942,8 +942,7 @@ class SimpleWorkflowSpec extends AbstractSpecification {
         workflowExecutor.restart(workflowInstanceId, false)
 
         then: "Ensure that an exception is thrown"
-        def exceptionThrown = thrown(ApplicationException)
-        exceptionThrown
+        thrown(NotFoundException.class)
 
         cleanup: "clean up the changes made to the task and workflow definition during start up"
         metadataService.updateTaskDef(integrationTask1Definition)
diff --git a/test-harness/src/test/groovy/com/netflix/conductor/test/resiliency/QueueResiliencySpec.groovy b/test-harness/src/test/groovy/com/netflix/conductor/test/resiliency/QueueResiliencySpec.groovy
index 1a04b59b63..2ef19708e0 100644
--- a/test-harness/src/test/groovy/com/netflix/conductor/test/resiliency/QueueResiliencySpec.groovy
+++ b/test-harness/src/test/groovy/com/netflix/conductor/test/resiliency/QueueResiliencySpec.groovy
@@ -20,7 +20,8 @@ import com.netflix.conductor.common.metadata.tasks.TaskResult
 import com.netflix.conductor.common.metadata.workflow.RerunWorkflowRequest
 import com.netflix.conductor.common.metadata.workflow.StartWorkflowRequest
 import com.netflix.conductor.common.run.Workflow
-import com.netflix.conductor.core.exception.ApplicationException
+import com.netflix.conductor.core.exception.NotFoundException
+import com.netflix.conductor.core.exception.TransientException
 import com.netflix.conductor.rest.controllers.TaskResource
 import com.netflix.conductor.rest.controllers.WorkflowResource
 import com.netflix.conductor.test.base.AbstractResiliencySpecification
@@ -65,8 +66,8 @@ class QueueResiliencySpec extends AbstractResiliencySpecification {
                 .withVersion(1))
 
         then: "Verify that workflow start fails with BACKEND_ERROR"
-        1 * queueDAO.push(*_) >> { throw new ApplicationException(ApplicationException.Code.BACKEND_ERROR, "Queue push failed from Spy") }
-        thrown(ApplicationException)
+        1 * queueDAO.push(*_) >> { throw new TransientException("Queue push failed from Spy") }
+        thrown(TransientException.class)
     }
 
     def "Verify terminate succeeds when QueueDAO is unavailable"() {
@@ -86,7 +87,7 @@ class QueueResiliencySpec extends AbstractResiliencySpecification {
         workflowResource.terminate(workflowInstanceId, "Terminated from a test")
 
         then: "Verify that terminate is successful without any exceptions"
-        2 * queueDAO.remove(*_) >> { throw new ApplicationException(ApplicationException.Code.BACKEND_ERROR, "Queue remove failed from Spy") }
+        2 * queueDAO.remove(*_) >> { throw new TransientException("Queue remove failed from Spy") }
         0 * queueDAO._
         with(workflowResource.getExecutionStatus(workflowInstanceId, true)) {
             status == Workflow.WorkflowStatus.TERMINATED
@@ -117,10 +118,10 @@ class QueueResiliencySpec extends AbstractResiliencySpecification {
         workflowResource.restart(workflowInstanceId, false)
 
         then: ""
-        1 * queueDAO.push(*_) >> { throw new ApplicationException(ApplicationException.Code.BACKEND_ERROR, "Queue push failed from Spy") }
-        1 * queueDAO.remove(*_) >> { throw new ApplicationException(ApplicationException.Code.BACKEND_ERROR, "Queue remove failed from Spy") }
+        1 * queueDAO.push(*_) >> { throw new TransientException("Queue push failed from Spy") }
+        1 * queueDAO.remove(*_) >> { throw new TransientException("Queue remove failed from Spy") }
         0 * queueDAO._
-        thrown(ApplicationException)
+        thrown(TransientException.class)
         with(workflowResource.getExecutionStatus(workflowInstanceId, true)) {
             status == Workflow.WorkflowStatus.TERMINATED
             tasks.size() == 0
@@ -150,9 +151,9 @@ class QueueResiliencySpec extends AbstractResiliencySpecification {
         workflowResource.rerun(workflowInstanceId, rerunWorkflowRequest)
 
         then: ""
-        1 * queueDAO.push(*_) >> { throw new ApplicationException(ApplicationException.Code.BACKEND_ERROR, "Queue push failed from Spy") }
+        1 * queueDAO.push(*_) >> { throw new TransientException("Queue push failed from Spy") }
         0 * queueDAO._
-        thrown(ApplicationException)
+        thrown(TransientException.class)
         with(workflowResource.getExecutionStatus(workflowInstanceId, true)) {
             status == Workflow.WorkflowStatus.TERMINATED
             tasks.size() == 0
@@ -180,9 +181,9 @@ class QueueResiliencySpec extends AbstractResiliencySpecification {
         workflowResource.retry(workflowInstanceId, false)
 
         then: "Verify retry fails"
-        1 * queueDAO.push(*_) >> { throw new ApplicationException(ApplicationException.Code.BACKEND_ERROR, "Queue push failed from Spy") }
+        1 * queueDAO.push(*_) >> { throw new TransientException("Queue push failed from Spy") }
         0 * queueDAO._
-        thrown(ApplicationException)
+        thrown(TransientException.class)
         with(workflowResource.getExecutionStatus(workflowInstanceId, true)) {
             status == Workflow.WorkflowStatus.TERMINATED
             tasks.size() == 1
@@ -259,7 +260,7 @@ class QueueResiliencySpec extends AbstractResiliencySpecification {
         workflowResource.getExecutionStatus(workflowInstanceId, true)
 
         then:
-        thrown(ApplicationException)
+        thrown(NotFoundException.class)
     }
 
     def "Verify decide succeeds when QueueDAO is unavailable"() {
@@ -340,8 +341,8 @@ class QueueResiliencySpec extends AbstractResiliencySpecification {
         workflowResource.resumeWorkflow(workflowInstanceId)
 
         then: "exception is thrown"
-        1 * queueDAO.push(*_) >> { throw new ApplicationException(ApplicationException.Code.BACKEND_ERROR, "Queue push failed from Spy") }
-        thrown(ApplicationException)
+        1 * queueDAO.push(*_) >> { throw new TransientException("Queue push failed from Spy") }
+        thrown(TransientException.class)
         with(workflowResource.getExecutionStatus(workflowInstanceId, true)) {
             status == Workflow.WorkflowStatus.PAUSED
             tasks.size() == 1
@@ -375,8 +376,8 @@ class QueueResiliencySpec extends AbstractResiliencySpecification {
         workflowResource.resetWorkflow(workflowInstanceId)
 
         then: "Verify an exception is thrown"
-        1 * queueDAO.resetOffsetTime(*_) >> { throw new ApplicationException(ApplicationException.Code.BACKEND_ERROR, "Queue resetOffsetTime failed from Spy") }
-        thrown(ApplicationException)
+        1 * queueDAO.resetOffsetTime(*_) >> { throw new TransientException("Queue resetOffsetTime failed from Spy") }
+        thrown(TransientException.class)
     }
 
     def "Verify search is not impacted by QueueDAO"() {
diff --git a/test-harness/src/test/groovy/com/netflix/conductor/test/util/WorkflowTestUtil.groovy b/test-harness/src/test/groovy/com/netflix/conductor/test/util/WorkflowTestUtil.groovy
index 4ba25b476d..0a1e383cab 100644
--- a/test-harness/src/test/groovy/com/netflix/conductor/test/util/WorkflowTestUtil.groovy
+++ b/test-harness/src/test/groovy/com/netflix/conductor/test/util/WorkflowTestUtil.groovy
@@ -23,7 +23,7 @@ import com.netflix.conductor.common.metadata.tasks.TaskDef
 import com.netflix.conductor.common.metadata.tasks.TaskResult
 import com.netflix.conductor.common.metadata.workflow.WorkflowDef
 import com.netflix.conductor.core.WorkflowContext
-import com.netflix.conductor.core.exception.ApplicationException
+import com.netflix.conductor.core.exception.NotFoundException
 import com.netflix.conductor.core.execution.WorkflowExecutor
 import com.netflix.conductor.dao.QueueDAO
 import com.netflix.conductor.model.WorkflowModel
@@ -204,12 +204,8 @@ class WorkflowTestUtil {
     Optional<TaskDef> getPersistedTaskDefinition(String taskDefName) {
         try {
             return Optional.of(metadataService.getTaskDef(taskDefName))
-        } catch (ApplicationException applicationException) {
-            if (applicationException.code == ApplicationException.Code.NOT_FOUND) {
-                return Optional.empty()
-            } else {
-                throw applicationException
-            }
+        } catch(NotFoundException nfe) {
+            return Optional.empty()
         }
     }