Idempotency: What, Why and How

A deep dive into idempotency for HTTP APIs, covering the theory and a practical Laravel implementation using the `wendelladriel/laravel-idempotency` package. Explains idempotency keys, request fingerprinting, cached response replay, atomic locks for concurrent requests, and key scoping (user/IP/global). Shows how to apply idempotency via route middleware or PHP attributes, customize per-endpoint settings, design idempotent controllers with proper domain invariants, handle failure status codes (400/409/422), use Artisan commands for observability, and write feature tests for retry contracts. Also covers common mistakes like reusing keys across operations or neglecting shared cache infrastructure.

#architecture

#php

#laravel

Apr 27•16m read time•From wendelladriel.com

Table of contents

Introduction What Idempotency Actually Is HTTP Methods and Idempotency Idempotency Is Not Deduplication Only The Moving Parts Installing the Package Applying Idempotency with Route Middleware Customizing an Endpoint Applying Idempotency with Attributes Generating Keys Designing Idempotent Controllers Choosing the Right Scope What Happens on Failures Observability and Maintenance Testing the Retry Contract Common Mistakes Conclusion