On-callMediumoc-g544

Subject Pool exhaustionLevel Entry–Mid~20 minCommon in Databases & SQL interviewsIndustries Technology, Software development

Question

A service that talks to a database starts intermittently failing requests with 'timeout acquiring connection from pool' errors, getting worse over a couple of hours after a deploy this morning. The database itself looks healthy (low CPU, normal query times). Traffic is normal. The pool dashboard shows in-use connections pinned at the max while idle connections sit at zero. How do you triage?

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.