The scenario
A Java service runs a fixed pool of 200 threads in a container limited to 2 CPUs, with an unbounded task queue in front. Under a traffic spike, latency climbs to 40 seconds and the heap fills with queued task objects.
What it tests
- Whether the candidate refuses to give a universal number
- Whether they reason from what the threads spend their time doing
- Whether they consider the downstream resources the pool feeds
Answer it out loud first. Recognising a good answer is not the same skill as producing one.