diff --git a/src/tateyama/transport/wire.h b/src/tateyama/transport/wire.h
index ea9ac14..feb23ac 100644
--- a/src/tateyama/transport/wire.h
+++ b/src/tateyama/transport/wire.h
@@ -1004,15 +1004,15 @@ class connection_queue
         index_queue(std::size_t size, boost::interprocess::managed_shared_memory::segment_manager* mgr) : queue_(mgr), capacity_(size) {
             queue_.resize(capacity_);
         }
-        void fill() {
+        void fill(std::uint8_t admin_slots) {
             for (std::size_t i = 0; i < capacity_; i++) {
                 queue_.at(i) = i;
             }
-            pushed_.store(capacity_);
+            pushed_.store(capacity_ - admin_slots);
         }
-        void push(std::size_t len) {
+        void push(std::size_t sid, std::size_t admin_slots = 0) {
             boost::interprocess::scoped_lock lock(mutex_);
-            queue_.at(index(pushed_.load())) = len;
+            queue_.at(index(pushed_.load() + admin_slots)) = sid;
             pushed_.fetch_add(1);
             std::atomic_thread_fence(std::memory_order_acq_rel);
             condition_.notify_one();
@@ -1020,7 +1020,18 @@ class connection_queue
         [[nodiscard]] std::size_t try_pop() {
             auto current = poped_.load();
             while (true) {
-                if (pushed_.load() == current) {
+                if (pushed_.load() <= current) {
+                    throw std::runtime_error("no request available");
+                }
+                if (poped_.compare_exchange_strong(current, current + 1)) {
+                    return queue_.at(index(current));
+                }
+            }
+        }
+        [[nodiscard]] std::size_t try_pop(std::uint8_t admin_slots) {
+            auto current = poped_.load();
+            while (true) {
+                if ((pushed_.load() + admin_slots) <= current) {
                     throw std::runtime_error("no request available");
                 }
                 if (poped_.compare_exchange_strong(current, current + 1)) {
@@ -1129,8 +1140,9 @@ class connection_queue
     /**
      * @brief Construct a new object.
      */
-    connection_queue(std::size_t n, boost::interprocess::managed_shared_memory::segment_manager* mgr) : q_free_(n, mgr), q_requested_(n, mgr), v_requested_(n, mgr) {
-        q_free_.fill();
+    connection_queue(std::size_t n, boost::interprocess::managed_shared_memory::segment_manager* mgr, std::uint8_t as_n)
+        : q_free_(n + as_n, mgr), q_requested_(n + as_n, mgr), v_requested_(n + as_n, mgr), admin_slots_(as_n) {
+        q_free_.fill(as_n);
     }
     ~connection_queue() = default;
 
@@ -1143,12 +1155,17 @@ class connection_queue
     connection_queue& operator = (connection_queue&&) = delete;
 
     std::size_t request() {
-        auto rid = q_free_.try_pop();
-        q_requested_.push(rid);
-        return rid;
+        auto sid = q_free_.try_pop();
+        q_requested_.push(sid);
+        return sid;
+    }
+    std::size_t request_admin() {
+        auto sid = q_free_.try_pop(admin_slots_);
+        q_requested_.push(sid);
+        return sid;
     }
-    std::size_t wait(std::size_t rid, std::int64_t timeout = 0) {
-        auto& entry = v_requested_.at(rid);
+    std::size_t wait(std::size_t sid, std::int64_t timeout = 0) {
+        auto& entry = v_requested_.at(sid);
         try {
             auto rtnv = entry.wait(timeout);
             entry.reuse();
@@ -1158,8 +1175,8 @@ class connection_queue
             throw ex;
         }
     }
-    bool check(std::size_t rid) {
-        return v_requested_.at(rid).check();
+    bool check(std::size_t sid) {
+        return v_requested_.at(sid).check();
     }
     std::size_t listen() {
         if (q_requested_.wait(terminate_)) {
@@ -1179,10 +1196,10 @@ class connection_queue
     void reject(std::size_t sid) {
         q_requested_.pop();
         v_requested_.at(sid).reject();
-        q_free_.push(sid);
+        q_free_.push(sid, admin_slots_);
     }
-    void disconnect(std::size_t rid) {
-        q_free_.push(rid);
+    void disconnect(std::size_t sid) {
+        q_free_.push(sid, admin_slots_);
     }
 
     // for terminate
@@ -1209,6 +1226,7 @@ class connection_queue
     boost::interprocess::vector<element, element_allocator> v_requested_;
 
     std::atomic_bool terminate_{false};
+    std::uint8_t admin_slots_;
     boost::interprocess::interprocess_semaphore s_terminated_{0};
 
     std::size_t session_id_{};
diff --git a/test/ogawayama/stub/server_wires_impl.h b/test/ogawayama/stub/server_wires_impl.h
index 5d6a8cb..8327990 100644
--- a/test/ogawayama/stub/server_wires_impl.h
+++ b/test/ogawayama/stub/server_wires_impl.h
@@ -429,7 +429,7 @@ class connection_container
             managed_shared_memory_ =
                 std::make_unique<boost::interprocess::managed_shared_memory>(boost::interprocess::create_only, name_.c_str(), request_queue_size);
             managed_shared_memory_->destroy<connection_queue>(connection_queue::name);
-            connection_queue_ = managed_shared_memory_->construct<connection_queue>(connection_queue::name)(n, managed_shared_memory_->get_segment_manager());
+            connection_queue_ = managed_shared_memory_->construct<connection_queue>(connection_queue::name)(n, managed_shared_memory_->get_segment_manager(), 1);
         }
         catch(const boost::interprocess::interprocess_exception& ex) {
             std::abort();  // FIXME