Skip to content

HTTP Semantics: Method Idempotency and Safety

Classifying operations by whether they are safe (no side effects) and idempotent (repeatable without different effect) enables caching, retry logic, and client optimization; these properties are semantic contracts independent of implementation.

Tension Addressed

Reliability vs. Latency (enables safe retries)

Recognizable As

GET vs. POST decisions, read vs. write operations, query vs. command separation (CQRS), idempotency keys in APIs

Canonical Sources

Fielding et al., RFC 7231 HTTP/1.1 Semantics (2014); Fielding REST dissertation (2000)

Transfers To

API design, database operations, distributed systems, CQRS, event sourcing, cache invalidation strategies

Sub-concepts: - Safe methods: Can be cached and prefetched freely - Idempotent methods: Can be retried automatically on failure - Non-idempotent operations: Require application-level deduplication if reliability is needed