Building Idempotent Event Consumers
Make choreography saga participants safe against duplicate and out-of-order events using idempotent consumers, the inbox pattern, and the outbox pattern.
Events Get Redelivered
In a choreography saga, services react to events from a broker. Brokers deliver at least once, so the same event can arrive twice — and sometimes out of order. Naive handlers double-charge or double-ship.
The Goal: Idempotent Consumers
An idempotent consumer can process the same event repeatedly with no extra effect. This is essential for correctness in any event-driven saga.
All lessons in this course
- Designing Event-Driven Sagas
- Event Bus and Message Brokers
- Handling Compensation with Events
- Building Idempotent Event Consumers