Debugging Idempotency Bugs
How to debug duplicate writes when clients, webhooks, or workers retry after ambiguous failures.
Pattern
A request or event can be delivered more than once, but the service performs the side effect each time.
warningSymptoms
- arrow_rightDuplicate orders or invoices
- arrow_rightRetries after timeouts create new resources
- arrow_rightWebhook replay changes state twice
searchWhere to look
- arrow_rightIdempotency key parsing
- arrow_rightProcessed-event store
- arrow_rightSide-effect ordering
- arrow_rightReplay response storage
buildCommon fixes
- arrow_rightPersist idempotency keys before side effects
- arrow_rightDeduplicate provider event ids
- arrow_rightReplay the first durable result
- arrow_rightAdd duplicate-delivery tests
Practice challenges
No ready practice incident is mapped yet.