Too many threads of type "SimpleAsyncTaskExecutor-" accumulating

I got to observe too many threads of type “SimpleAsyncTaskExecutor-” getting accumulated while running Fineract with increased concurrent users (ranging from 200-1000 users at a time performing saving deposits across 5 pod replication).

When deployed in a Kubernetes environment with read/write pods separated, the accumulation of threads within the pods is causing the resource exhaustion and JVM freeze.

From a quick java thread-dump walk-through, my understanding is that these threads are created in the process of business event notification post write commands (like savings deposit) and is required by design.  Raising this observation to see if it can be optimized to reduce the number of threads getting generated per transaction.

From one of the thread dumps of a pod, we observed 168 threads of type “https-jsse-nio2-8443-exec-“ and “SimpleAsyncTaskExecutor-“ were 320.