Connection pool storms after failover
Aurora MySQL. A 20-second primary failover happened at 14:00. The DB recovered, but for the next 8 minutes the new primary sat at `Threads_connected` = max_connections, CPU pegged, and the app threw 'too many connections' even though real query volume was normal. App tier is ~200 stateless pods, each with a 20-connection HikariCP pool and aggressive reconnect-on-error. Connections that *do* get in run fast. Walk through what happened and how you'd both recover now and prevent it.
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 35 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.