Hi Sergei, Since MDEV-5533 is marked critical for 10.0.12 it is a good time to start this discussion. IIRC we agreed that our intention is to accept default value change for thread_pool_max_threads into 10.0 and accept priority queue throttling into 10.1. So default value for thread_pool_max_threads has bumped in percona server from 500 to 100 000. The reason is: deadlocks and uneven distribution of worker threads between thread groups in case of stalled connections. But the above is contradicting to suggestions in KB: https://mariadb.com/kb/en/threadpool-in-55/ ... so ideally, there should be a single active thread for each CPU on the machine. ... If your application constantly pegs at 500 threads, it might be a strong indicator for high contention in the application, and threadpool does not help much. ... One way to solve the problem would be to set thread_pool_max_threads to a very high value, but this might be less than ideal, and negatively affect performance. ... Said the above, do you still think it is a good idea to raise default value of thread_pool_max_threads? If so, what should KB article state wrt this variable? Thanks, Sergey