On-callMediumoc-g004

Subject Database incidentsLevel Mid–Senior~30 minCommon in Databases & SQL · Reliability & on-call interviewsIndustries Technology, Software development

Question

A customer-facing analytics dashboard on Postgres started loading in 12s instead of 300ms at 11:00, and a handful of pages now 504. pg_stat_statements shows one query — a filter on tickets WHERE org_id = $1 AND created_at > $2 ORDER BY created_at DESC LIMIT 50 — jumped from 5ms mean to 4s mean and is now the top query by total time. A large new enterprise customer was onboarded yesterday with ~30M tickets, 10x the next biggest org. No code or schema changed. 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.