IntermediateScenario
10 min
Thread Pool Exhaustion Causing Latency
PerformanceConcurrencyAPIs
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Interview Question
Sudden latency spikes correlate with saturated server thread pools. How do you diagnose and remediate safely?
Key Points to Cover
- Instrument busy/queued threads, queue length, and wait times
- Identify blocking operations and synchronous I/O
- Right-size pools; introduce async/IO multiplexing where safe
- Apply backpressure/timeouts to avoid unbounded queues
- Load test and validate new pool sizes under peak patterns
Evaluation Rubric
Uses the right thread/queue metrics30% weight
Finds blocking operations30% weight
Balances pool sizing and backpressure20% weight
Verifies with representative load20% weight
Hints
- 💡Beware of deadlocks after pool changes.
Common Pitfalls to Avoid
- ⚠️Blindly increasing thread pool size without understanding the root cause, leading to increased context switching overhead and resource contention.
- ⚠️Failing to identify and address the actual blocking operations, rendering thread pool adjustments ineffective.
- ⚠️Implementing asynchronous patterns without adequate understanding, potentially introducing new complexities or bugs.
- ⚠️Not considering the resource implications of asynchronous operations or I/O multiplexing on other system components.
- ⚠️Neglecting the importance of proper error handling and graceful degradation, which can exacerbate the impact of saturated thread pools during high load.
Potential Follow-up Questions
- ❓How to avoid priority inversion?
- ❓What about CPU vs IO-bound pools?
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