On-callMediumoc-g258

Subject SaturationLevel Mid–Senior~30 minCommon in Reliability & on-call interviewsIndustries Technology, Software development

Question

A latency-sensitive Go service in Kubernetes shows periodic p99 latency spikes every ~100ms and elevated tail latency under load, yet the pod's reported CPU usage averages only ~40% of its limit and the node has spare capacity. The container has `limits.cpu: 2` and `requests.cpu: 0.5`. GOMAXPROCS is left at the node's core count (32). The spikes got worse after the cluster moved to higher-core nodes. How do you triage and fix?

What a strong answer looks like

Stop the bleeding first (mitigate), then form hypotheses from real signals. Separate root cause from symptom, communicate status as you go, and close with what prevents a repeat.

Learn the concepts

Diagram & narrate the incident

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Run or narrate your approach, then ask the coach.