Connection pool saturation under load
Your API tier autoscales beautifully and stays at ~40% CPU through a marketing-driven 3x surge, yet p99 climbs and `pool timeout: could not acquire connection within 5000ms` errors appear at the app. Each pod has an HTTP client pool to a downstream `pricing` service sized at 20 connections — a number chosen long ago to match steady-state concurrency. The downstream `pricing` service itself reports normal latency and is not saturated. Pods are plentiful. How do you triage and mitigate this surge-time failure?
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.
0:00 of about 25 min
Which questions mattered is sealed until you submit. Telling you now would just be handing over the edge cases.
Run or narrate your approach, then ask the coach.