Currently the ExecutorService used for this is as such:

ExecutorService executorService = new ThreadPoolExecutor(0, Integer.MAX_VALUE, Long.MAX_VALUE, TimeUnit.MILLISECONDS, new SynchronousQueue<>(), new AsyncIOThreadFactory());

This means that the threads never terminate and are spawned whenever a thread is not available, which for a server under a spike of load spawns many threads which never exit, consuming system resources indefinitely.

I would suggest that a saner idle timeout than Long.MAX_VALUE should be used, such as 60 seconds, unless there is a good reason I am unaware of as to why such threads should never die.