The keep-alive time for extra idle threads is in milliseconds. Once this time has elapsed for an idle thread, it will be destroyed. This parameter is applicable only if the Iterate or the Clone mediator is used to handle a high load. You can increase the number of threads specified via this parameter as required to balance an increased load.
You can use this parameter to specify the length of the queue that is used to hold the runnable tasks to be executed by the pool. You can specify a finite value as the queue length by giving any positive number. If this parameter is set to (-1) it means that the task queue length is infinite.
If the queue length is finite there can be situations where requests are rejected when the task queue is full, and all the cores are occupied. If the queue length is infinite, and if some thread locking happens, the server can go out of memory. Therefore, you need to decide on an optimal value based on the actual load.