How to use this reference
Editorial synthesis: distinguish who may act, which logical operation is being repeated and what state was committed. Document identity scope, retention assumptions and response meaning. A request ID does not confer authority. Preventing duplicate effects does not guarantee eventual success or establish end-to-end exactly-once delivery. Keep each integration's completion and authorization responsibilities explicit.
Before reading
- Basic familiarity with API requests, distributed failures and application state transitions
Context and limits
- AIP-155 permits APIs to add request IDs and says they should be optional. The ID belongs to the request, not the resource. Its guarantees apply to the service's documented contract, not every API.
- The current-state response exception applies when reproducing the historical success response is infeasible. Idempotent effects do not require byte-identical response data.
- Caller scoping, changed-parameter rejection and coordinated identity/effect recording are AWS guidance, not explicit AIP-155 requirements. AWS describes service-dependent retention; it does not prescribe a universal lifetime.
- AIP-155's Created and Updated headers both display 2019-05-06. The corresponding first-party commit is timestamped 2024-01-26T17:45:54Z but adds a 2024-01-08 changelog entry. These are distinct maintenance signals, not new 2026 guidance.
- Authorization separation and completion limits are editorial synthesis. This resource establishes no incident, affected deployment, bounty, implementation correctness, current exposure or testing authorization.
Sources and provenance
- AIP-155: Request identification Google · reviewed 2026-10-04
- Making retries safe with idempotent APIs Amazon Web Services · reviewed 2026-10-04
- AIP-155: correct the request message and add a changelog entry Google AIP maintainers · reviewed 2026-10-04
Record reviewed 2026-10-04. Snapshot 53796974ace8. Open the complete JSON contract.