@Override
  protected void initializeMessageQueue(String id, boolean cleanQueues) {
    // Create the region name
    String regionName = id + "_SERIAL_GATEWAY_SENDER_QUEUE";

    final SerialSecondaryGatewayListener listener = getAndInitializeCacheListener();

    // Create the region queue
    queue = new SerialGatewaySenderQueue(sender, regionName, listener, cleanQueues);

    if (logger.isDebugEnabled()) {
      logger.debug("Created queue: {}", queue);
    }
  }
When the Number of unchecked events exceeds this threshold and the number of tokens in the map
exceeds this threshold then a check will be done for old tokens.
geode-core/src/main/java/org/apache/geode/internal/cache/wan/serial/SerialGatewaySenderEventProcessor.java