Code Room
On-callMediumoc-g045
Subject Bad rolloutLevel Mid–Senior~30 minCommon in Reliability & on-call interviewsIndustries Technology, Software development

Question

At 14:02 you deploy v412 of the checkout API (a Java/Spring service behind 12 pods). Within 4 minutes p99 latency on /checkout climbs from 180ms to 9s and the error rate ticks to 6% with 'connection timeout acquiring from pool' in logs. The DB CPU dashboard is flat at 40%. Active DB connections jumped from ~120 to the configured max of 200 and are pinned there. The only thing in v412's diff is a new audit-write that runs inside the same request transaction. Walk me through how you triage and mitigate.

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.

Diagram & narrate the incident
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Run or narrate your approach, then ask the coach.