diff --git a/lib/ClientImpl.cc b/lib/ClientImpl.cc
index 043d6d42..acac66c2 100644
--- a/lib/ClientImpl.cc
+++ b/lib/ClientImpl.cc
@@ -78,11 +78,12 @@ void invokeLegacyCallback(const std::function<void(Result, T)>& callback,
 
 static const char hexDigits[] = {'0', '1', '2', '3', '4', '5', '6', '7',
                                  '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};
-static std::uniform_int_distribution<> hexDigitsDist(0, sizeof(hexDigits) - 1);
-static std::mt19937 randomEngine =
-    std::mt19937(std::chrono::high_resolution_clock::now().time_since_epoch().count());
 
 std::string generateRandomName() {
+    // Called concurrently by all the clients of the process, so the generator state must not be shared.
+    thread_local std::uniform_int_distribution<> hexDigitsDist(0, sizeof(hexDigits) - 1);
+    thread_local std::mt19937 randomEngine(std::random_device{}());
+
     const int randomNameLength = 10;
 
     std::string randomName;
diff --git a/lib/ConnectionPool.h b/lib/ConnectionPool.h
index 201c1d01..8acfa329 100644
--- a/lib/ConnectionPool.h
+++ b/lib/ConnectionPool.h
@@ -96,7 +96,11 @@ class PULSAR_PUBLIC ConnectionPool {
         return getConnectionAsync(address, address);
     }
 
-    size_t generateRandomIndex() { return randomDistribution_(randomEngine_); }
+    size_t generateRandomIndex() {
+        // Handlers are created concurrently from the caller and executor threads.
+        std::lock_guard<std::mutex> lock(randomMutex_);
+        return randomDistribution_(randomEngine_);
+    }
 
    private:
     const AtomicSharedPtr<ServiceInfo>& serviceInfo_;
@@ -110,6 +114,7 @@ class PULSAR_PUBLIC ConnectionPool {
 
     std::uniform_int_distribution<> randomDistribution_;
     std::mt19937 randomEngine_;
+    std::mutex randomMutex_;
 
     auto releaseConnections() {
         decltype(pool_) pool;