diff --git a/cdk/bin/cdk.ts b/cdk/bin/cdk.ts
index 13a0527..843d76a 100644
--- a/cdk/bin/cdk.ts
+++ b/cdk/bin/cdk.ts
@@ -2,7 +2,7 @@
 import 'source-map-support/register';
 import * as cdk from 'aws-cdk-lib';
 import { CdkStack } from '../lib/cdk-stack';
-import { getDeploymentStage } from '../lib/deployment-stage';
+import { getDeploymentStage } from 'cdk-common';
 
 const app = new cdk.App();
 const deploymentStage = getDeploymentStage(app.node);
diff --git a/cdk/lib/cdk-stack.ts b/cdk/lib/cdk-stack.ts
index 467e05d..a9e3398 100644
--- a/cdk/lib/cdk-stack.ts
+++ b/cdk/lib/cdk-stack.ts
@@ -3,7 +3,7 @@ import { Construct } from 'constructs';
 
 import { ContentsBucket } from './contents-bucket';
 import { ContentsDistribution } from './contents-distribution';
-import { DeploymentStage } from './deployment-stage';
+import { DeploymentStage } from 'cdk-common';
 
 type Props = StackProps & Readonly<{
   // Deployment stage.
diff --git a/cdk/lib/contents-bucket.ts b/cdk/lib/contents-bucket.ts
index 9eb88aa..4443ffd 100644
--- a/cdk/lib/contents-bucket.ts
+++ b/cdk/lib/contents-bucket.ts
@@ -1,7 +1,7 @@
 import { RemovalPolicy, aws_s3 as s3 } from 'aws-cdk-lib';
 import { Construct } from 'constructs';
 
-import { DeploymentStage } from './deployment-stage';
+import { DeploymentStage } from 'cdk-common';
 
 type Props = Readonly<{
   // Deployment stage.
diff --git a/cdk/lib/contents-distribution.ts b/cdk/lib/contents-distribution.ts
index 69932e5..1cf106e 100644
--- a/cdk/lib/contents-distribution.ts
+++ b/cdk/lib/contents-distribution.ts
@@ -13,7 +13,7 @@ import {
   CODEMONGER_CERTIFICATE_ARN,
 } from './certificate-config';
 import { ContentsBucket } from './contents-bucket';
-import { DeploymentStage } from './deployment-stage';
+import { DeploymentStage } from 'cdk-common';
 
 type Props = Readonly<{
   // S3 bucket for contents of the codemonger website.
diff --git a/cdk/lib/deployment-stage.ts b/cdk/lib/deployment-stage.ts
deleted file mode 100644
index 7a57d20..0000000
--- a/cdk/lib/deployment-stage.ts
+++ /dev/null
@@ -1,52 +0,0 @@
-import { Node } from 'constructs';
-
-/** Possible deployment stages. */
-export const DEPLOYMENT_STAGES = ['development', 'production'] as const;
-
-/** Deployment stage type. */
-export type DeploymentStage = typeof DEPLOYMENT_STAGES[number];
-
-/** Name of the CDK context value for the deployment stage. */
-export const DEPLOYMENT_STAGE_CDK_CONTEXT = 'codemonger:stage';
-
-/**
- * Converts a given string into an equivalent deployment stage.
- *
- * Case-insensitive.
- *
- * @throws RangeError
- *
- *   If `stageStr` is invalid deployment stage.
- */
-export function asDeploymentStage(stageStr: string): DeploymentStage {
-  const stageStrL = stageStr.toLowerCase();
-  for (const stage of DEPLOYMENT_STAGES) {
-    if (stage === stageStrL) {
-      return stage;
-    }
-  }
-  throw new RangeError(`invalid deployment stage: ${stageStr}`);
-}
-
-/**
- * Returns the deployment stage specified to the CDK context.
- *
- * The deployment stage must be specified to the `"codemonger:stage"` CDK
- * context value.
- *
- * @param node
- *
- *   CDK construct node that provides the CDK context.
- *
- * @throws RangeError
- *
- *   If no deployment stage is specified,
- *   or the specified deployment stage is invalid.
- */
-export function getDeploymentStage(node: Node): DeploymentStage {
-  const stage = node.tryGetContext(DEPLOYMENT_STAGE_CDK_CONTEXT);
-  if (typeof stage !== 'string') {
-    throw new RangeError(`invalid deployment stage: ${stage}`);
-  }
-  return asDeploymentStage(stage);
-}