Preventing Duplicate Webhook Processing Under Concurrent Load with Database Locks

Deduplicating asynchronous webhooks with a simple check-then-insert pattern can fail when retries arrive simultaneously, because multiple threads may read a missing record before any of them commits. This race condition can lead to duplicate processing of downstream actions such as balance updates or order provisioning. The article argues that true idempotency requires database-level safeguards, including explicit transaction isolation or immediate exclusive locks. It also recommends unique constraints as a final fallback and jittered exponential backoff to handle lock contention.