diff --git a/include/ccapi_cpp/ccapi_event_dispatcher.h b/include/ccapi_cpp/ccapi_event_dispatcher.h
index 09a7da8a..edff1dc0 100644
--- a/include/ccapi_cpp/ccapi_event_dispatcher.h
+++ b/include/ccapi_cpp/ccapi_event_dispatcher.h
@@ -13,7 +13,7 @@
 namespace ccapi {
 class EventDispatcher final {
  public:
-  explicit EventDispatcher(size_t numDispatcherThreads = 1)
+  explicit EventDispatcher(const size_t numDispatcherThreads = 1)
       : numDispatcherThreads(numDispatcherThreads) {
     CCAPI_LOGGER_FUNCTION_ENTER;
     CCAPI_LOGGER_TRACE("numDispatcherThreads = "+size_tToString(numDispatcherThreads));
diff --git a/include/ccapi_cpp/ccapi_event_queue.h b/include/ccapi_cpp/ccapi_event_queue.h
deleted file mode 100644
index dd5519e8..00000000
--- a/include/ccapi_cpp/ccapi_event_queue.h
+++ /dev/null
@@ -1,51 +0,0 @@
-#ifndef INCLUDE_CCAPI_CPP_CCAPI_EVENT_QUEUE_H_
-#define INCLUDE_CCAPI_CPP_CCAPI_EVENT_QUEUE_H_
-#include <queue>
-#include <mutex>
-#include <vector>
-#include <condition_variable>
-#include "ccapi_cpp/ccapi_event.h"
-namespace ccapi {
-class EventQueue final {
- public:
-  void push(Event&& event) {
-    {
-      std::lock_guard<std::mutex> lock(this->lock);
-      if (this->maxSize == -1 || this->queue.size() < this->maxSize) {
-        CCAPI_LOGGER_TRACE("this->queue.size() = "+size_tToString(this->queue.size()));
-        this->queue.push_back(event);
-      } else {
-        CCAPI_LOGGER_WARN("event queue is full!");
-      }
-    }
-    this->cv.notify_all();
-  }
-  Event& front() {
-    std::lock_guard<std::mutex> lock(this->lock);
-    return this->queue.front();
-  }
-  std::vector<Event> purge() {
-    std::lock_guard<std::mutex> lock(this->lock);
-    std::vector<Event> p;
-    std::swap(p, this->queue);
-    return p;
-  }
-  size_t size() const {
-    std::lock_guard<std::mutex> lock(this->lock);
-    return this->queue.size();
-  }
-  size_t getMaxSize() const {
-    return maxSize;
-  }
-  void setMaxSize(size_t maxSize) {
-    this->maxSize = maxSize;
-  }
-  std::condition_variable cv;
-
- private:
-  std::vector<Event> queue;
-  mutable std::mutex lock;
-  size_t maxSize{};
-};
-} /* namespace ccapi */
-#endif  // INCLUDE_CCAPI_CPP_CCAPI_EVENT_QUEUE_H_
diff --git a/include/ccapi_cpp/ccapi_exchange.h b/include/ccapi_cpp/ccapi_macro.h
similarity index 97%
rename from include/ccapi_cpp/ccapi_exchange.h
rename to include/ccapi_cpp/ccapi_macro.h
index 8c766412..3026466b 100644
--- a/include/ccapi_cpp/ccapi_exchange.h
+++ b/include/ccapi_cpp/ccapi_macro.h
@@ -1,5 +1,5 @@
-#ifndef INCLUDE_CCAPI_CPP_CCAPI_EXCHANGE_H_
-#define INCLUDE_CCAPI_CPP_CCAPI_EXCHANGE_H_
+#ifndef INCLUDE_CCAPI_CPP_CCAPI_MACRO_H_
+#define INCLUDE_CCAPI_CPP_CCAPI_MACRO_H_
 #define CCAPI_EXCHANGE_NAME_MARKET_DEPTH "MARKET_DEPTH"
 #define CCAPI_EXCHANGE_NAME_TRADE "TRADE"
 #ifndef CCAPI_EXCHANGE_NAME_MARKET_DEPTH_MAX
@@ -118,4 +118,4 @@
 #define CCAPI_EXCHANGE_NAME_CONNECTION "connection"
 #define CCAPI_EXCHANGE_NAME_REASON "reason"
 #define CCAPI_EXCHANGE_NAME_ERROR_MESSAGE "message"
-#endif  // INCLUDE_CCAPI_CPP_CCAPI_EXCHANGE_H_
+#endif  // INCLUDE_CCAPI_CPP_CCAPI_MACRO_H_
diff --git a/include/ccapi_cpp/ccapi_market_data_service.h b/include/ccapi_cpp/ccapi_market_data_service.h
index 446ee2da..6704db1b 100644
--- a/include/ccapi_cpp/ccapi_market_data_service.h
+++ b/include/ccapi_cpp/ccapi_market_data_service.h
@@ -14,7 +14,7 @@
 #include "websocketpp/common/connection_hdl.hpp"
 #include "ccapi_cpp/ccapi_event.h"
 #include "ccapi_cpp/ccapi_subscription_list.h"
-#include "ccapi_cpp/ccapi_exchange.h"
+#include "ccapi_cpp/ccapi_macro.h"
 #include "ccapi_cpp/ccapi_market_data_message.h"
 #include "rapidjson/document.h"
 #include "rapidjson/writer.h"
diff --git a/include/ccapi_cpp/ccapi_queue.h b/include/ccapi_cpp/ccapi_queue.h
new file mode 100644
index 00000000..085648c9
--- /dev/null
+++ b/include/ccapi_cpp/ccapi_queue.h
@@ -0,0 +1,55 @@
+#ifndef INCLUDE_CCAPI_CPP_CCAPI_QUEUE_H_
+#define INCLUDE_CCAPI_CPP_CCAPI_QUEUE_H_
+#include <queue>
+#include <mutex>
+#include <vector>
+#include "ccapi_cpp/ccapi_logger.h"
+namespace ccapi {
+template <class T>
+class Queue {
+ public:
+  std::string EXCEPTION_QUEUE_FULL = "queue is full";
+  std::string EXCEPTION_QUEUE_EMPTY = "queue is empty";
+  explicit Queue(const size_t maxSize = 0)
+        : maxSize(maxSize) {}
+  void pushBack(T&& t) {
+    std::lock_guard<std::mutex> lock(this->m);
+    if (this->maxSize <= 0 || this->queue.size() < this->maxSize) {
+      CCAPI_LOGGER_TRACE("this->queue.size() = "+size_tToString(this->queue.size()));
+      this->queue.push_back(t);
+    } else {
+      CCAPI_LOGGER_FATAL(EXCEPTION_QUEUE_FULL);
+    }
+  }
+  T popBack() {
+    std::lock_guard<std::mutex> lock(this->m);
+    if (this->queue.empty()) {
+      CCAPI_LOGGER_FATAL(EXCEPTION_QUEUE_EMPTY);
+    } else {
+      T t = std::move(this->queue.back());
+      this->queue.pop_back();
+      return t;
+    }
+  }
+  std::vector<T> purge() {
+    std::lock_guard<std::mutex> lock(this->m);
+    std::vector<T> p;
+    std::swap(p, this->queue);
+    return p;
+  }
+  size_t size() const {
+    std::lock_guard<std::mutex> lock(this->m);
+    return this->queue.size();
+  }
+  bool empty() const {
+    std::lock_guard<std::mutex> lock(this->m);
+    return this->queue.empty();
+  }
+
+ private:
+  std::vector<T> queue;
+  mutable std::mutex m;
+  size_t maxSize{};
+};
+} /* namespace ccapi */
+#endif  // INCLUDE_CCAPI_CPP_CCAPI_QUEUE_H_
diff --git a/include/ccapi_cpp/ccapi_session.h b/include/ccapi_cpp/ccapi_session.h
index 9abec731..5fd76ece 100644
--- a/include/ccapi_cpp/ccapi_session.h
+++ b/include/ccapi_cpp/ccapi_session.h
@@ -42,8 +42,8 @@
 #include <vector>
 #include <map>
 #include <unordered_set>
-#include "ccapi_cpp/ccapi_event_queue.h"
-#include "ccapi_cpp/ccapi_exchange.h"
+#include "ccapi_cpp/ccapi_queue.h"
+#include "ccapi_cpp/ccapi_macro.h"
 #include "ccapi_cpp/ccapi_event_dispatcher.h"
 #include "ccapi_cpp/ccapi_event_handler.h"
 #include "ccapi_cpp/ccapi_event.h"
@@ -56,7 +56,8 @@ class Session final {
       : sessionOptions(options),
         sessionConfigs(configs),
         eventHandler(eventHandler),
-        eventDispatcher(eventDispatcher) {
+        eventDispatcher(eventDispatcher),
+        eventQueue(options.maxEventQueueSize) {
     CCAPI_LOGGER_FUNCTION_ENTER;
     if (this->eventHandler) {
       if (!this->eventDispatcher) {
@@ -67,7 +68,6 @@ class Session final {
         throw std::runtime_error("undefined behavior");
       }
     }
-    this->eventQueue.setMaxSize(options.maxEventQueueSize);
     CCAPI_LOGGER_FUNCTION_EXIT;
   }
 //  bool openService(std::string serviceName = "") {
@@ -151,7 +151,7 @@ class Session final {
     if (this->eventDispatcher) {
       this->eventDispatcher->start();
     }
-    std::function<void(Event& event)> wsEventHandler = std::bind(&Session::onEvent, this, std::placeholders::_1);
+    std::function<void(Event& event)> wsEventHandler = std::bind(&Session::onEvent, this, std::placeholders::_1, nullptr);
     auto sessionOptions = this->sessionOptions;
     auto sessionConfigs = this->sessionConfigs;
     CCAPI_LOGGER_TRACE("sessionOptions.enableOneIoContextPerExchange = "+toString(sessionOptions.enableOneIoContextPerExchange));
@@ -327,10 +327,10 @@ class Session final {
     }
     CCAPI_LOGGER_FUNCTION_EXIT;
   }
-  void onEvent(Event& event) {
+  void onEvent(Event& event, Queue<Event> *eventQueue) {
     CCAPI_LOGGER_FUNCTION_ENTER;
     CCAPI_LOGGER_TRACE("event = "+toString(event));
-    if (this->eventHandler) {
+    if (this->eventHandler && !eventQueue) {
       CCAPI_LOGGER_TRACE("handle event asynchronously");
       this->eventDispatcher->dispatch([&, event] {
         bool shouldContinue = true;
@@ -346,11 +346,15 @@ class Session final {
       });
     } else {
       CCAPI_LOGGER_TRACE("handle event synchronously");
-      this->eventQueue.push(std::move(event));
+      if (eventQueue) {
+        eventQueue->pushBack(std::move(event));
+      } else {
+        this->eventQueue.pushBack(std::move(event));
+      }
     }
     CCAPI_LOGGER_FUNCTION_EXIT;
   }
-  EventQueue eventQueue;
+  Queue<Event> eventQueue;
 
  private:
 //  std::string serviceName;
diff --git a/include/ccapi_cpp/ccapi_session_configs.h b/include/ccapi_cpp/ccapi_session_configs.h
index 01b2a0e3..3f31d8d5 100644
--- a/include/ccapi_cpp/ccapi_session_configs.h
+++ b/include/ccapi_cpp/ccapi_session_configs.h
@@ -1,10 +1,10 @@
 #ifndef INCLUDE_CCAPI_CPP_CCAPI_SESSION_CONFIGS_H_
 #define INCLUDE_CCAPI_CPP_CCAPI_SESSION_CONFIGS_H_
+#include "ccapi_cpp/ccapi_macro.h"
 #include <string>
 #include <map>
 #include <vector>
 #include <set>
-#include "ccapi_cpp/ccapi_exchange.h"
 #include "ccapi_cpp/ccapi_logger.h"
 namespace ccapi {
 class SessionConfigs final {
diff --git a/include/ccapi_cpp/ccapi_session_options.h b/include/ccapi_cpp/ccapi_session_options.h
index c7dfd8bc..b509cb4a 100644
--- a/include/ccapi_cpp/ccapi_session_options.h
+++ b/include/ccapi_cpp/ccapi_session_options.h
@@ -26,7 +26,7 @@ class SessionOptions final {
   bool enableOneIoContextPerExchange{};
   long pingIntervalMilliSeconds{10000};
   long pongTimeoutMilliSeconds{5000};
-  long maxEventQueueSize{-1};
+  long maxEventQueueSize{0};
 };
 } /* namespace ccapi */
 #endif  // INCLUDE_CCAPI_CPP_CCAPI_SESSION_OPTIONS_H_
diff --git a/include/ccapi_cpp/ccapi_subscription.h b/include/ccapi_cpp/ccapi_subscription.h
index 9ea59444..925e60d7 100644
--- a/include/ccapi_cpp/ccapi_subscription.h
+++ b/include/ccapi_cpp/ccapi_subscription.h
@@ -1,9 +1,9 @@
 #ifndef INCLUDE_CCAPI_CPP_CCAPI_SUBSCRIPTION_H_
 #define INCLUDE_CCAPI_CPP_CCAPI_SUBSCRIPTION_H_
+#include "ccapi_cpp/ccapi_macro.h"
 #include <string>
 #include <set>
 #include "ccapi_cpp/ccapi_correlationId.h"
-#include "ccapi_cpp/ccapi_exchange.h"
 #include "ccapi_cpp/ccapi_util.h"
 namespace ccapi {
 class Subscription final {