System Design
Advanced
Idempotency, Sagas, and Recovery
Coordinate multi-step workflows without relying on fragile distributed transactions.
35 min
3 sections
idempotency
sagas
recovery
1
2
3
01. Treat retries as normal
Section 1 of 3
Retries happen after client timeouts, worker restarts, broker redelivery, and failover. Every handler that performs side effects should be safe to run more than once or detect duplicate work.
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Payment capture handler:
1. Validate order is payable.
2. Check payment_attempt by idempotency_key.
3. If existing terminal result, return it.
4. Call provider with same idempotency key.
5. Store provider response.
6. Emit PaymentCaptured or PaymentFailed once.Back to Course