Client retry amplifies traffic surge
A mobile-app release this week added an aggressive client-side retry to a flaky-feeling endpoint. Today a genuine 2x organic surge hits and your backend, which has handled larger real surges before, falls over: it's pinned at 100% CPU, the load balancer shows incoming request rate ~7x baseline (far above the 2x of real users), and a chunk of that is duplicate requests carrying the same idempotency key seconds apart. Pulling the app open-rate, actual user activity is only up ~2x. 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.