On-callMediumoc-g523

Subject Quota exhaustionLevel Mid–Senior~25 minCommon in Reliability & on-call interviewsIndustries Technology

Question

Your product calls a third-party AI/maps API using a single shared API key with a per-key quota of 60,000 requests/minute. For months you're fine. A new feature shipped Monday that makes 4 calls per page view instead of 1, and on Wednesday a moderate traffic bump pushes you over the per-minute quota for the first time: you see a wall of 429 `quota exceeded` from the provider, user-facing features fail, and your own service CPU is fine. How do you triage and mitigate, and what's the durable 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.