Postgres replica CPU spike from unoptimized query
At 12:40 your reporting service's Postgres read replica spikes to 100% CPU and stays there; every query on that replica times out. pg_stat_activity shows one query running for 14 minutes that the app never normally runs that long: a user-built ad-hoc report joining three large tables with a LIKE '%...%' free-text filter and no LIMIT, generated by a new self-serve report builder shipped this morning. The same query keeps reappearing because the user keeps hitting 'retry' after each timeout. How do 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.
0:00 of about 30 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.