Zar Labs
Workflow idempotency patterns
Last reviewed: 2026-09-28
Executive summary
Distributed systems are at-least-once. Design idempotent handlers with idempotency keys and dedupe stores so retries are safe.
Patterns
- Idempotency keys on writes
- Dedupe tables / caches
- Transactional outbox
- Poison message handling
Pros & cons
Pros
- Safe retries
- Fewer duplicate side effects
Cons / watch-outs
- Extra storage and design
Comparison
| Delivery | Handler requirement |
|---|---|
| At-least-once | Must be idempotent |
| Exactly-once (claimed) | Still verify side effects |
Frequently asked questions
Do you design idempotent integrations?
Yes — standard on orchestration and SAP/CRM sync work. See /services/workflow-orchestration.
Ready to scope your build?
Share goals, stack constraints, and timeline. We’ll respond with a discovery path and phased estimate.