Idempotency

Technical explanation

In HTTP, a method is idempotent when multiple identical requests have the same intended effect as one request, although each response or side effect such as logging may differ. GET, HEAD, PUT and DELETE have idempotent semantics; APIs can also use idempotency keys to protect retried non-idempotent requests.

Business relevance

Idempotent operations make integrations, payment flows and automations safer to retry after timeouts or network failures, reducing duplicate records, charges and manual reconciliation.

Implementation example

An order API accepts an idempotency key with a create-order request, stores the first result, and returns that result when the client retries the same request.

Limitations and common misconceptions

Idempotency does not mean that every response is identical, that execution happens only once, or that concurrent requests are automatically safe. Key scope, retention, input matching and transactional boundaries must be designed explicitly.

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