Node.js · Senior · Question 10 of 75

p99 latency is high but average CPU usage is low. What might be the cause?

1The server has too much RAM
2Too few log lines
✓Correct answer: Occasional event loop blocking (big synchronous tasks, long GC pauses) that delays every request waiting in the queue

Explanation

Measure event loop delay with monitorEventLoopDelay. Short CPU spikes don't show up in average CPU but stall all concurrent requests.

Further reading

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