Question

During a flash sale, the app starts returning 500s and logs fill with "FATAL: sorry, too many clients already" and "remaining connection slots are reserved." Postgres `max_connections` is 200. The dashboard shows `pg_stat_activity` near 200 connections, but most are in state `idle in transaction` or plain `idle`, not actually running queries — DB CPU is low. The app runs 30 Kubernetes pods that just autoscaled from 8, each with its own connection pool sized at 20. No PgBouncer in front. A new feature shipped last week that opens a transaction early in a request handler. Triage and mitigate.