REST API Design

A good interface feels obvious. A poor one costs its users hours of guessing, double charges after a timeout and a support queue full of the same question. This book walks through the decisions behind HTTP interfaces that behave predictably: modelling resources, choosing methods and status codes, making retries safe with idempotency keys, paginating with cursors, filtering and sorting, returning errors in the standard problem details format, using cache validators, signalling rate limits, designing authentication and scopes, versioning without breaking clients, and writing the OpenAPI contract before the code. Every example was run against a small online-shop service, so the requests and responses are real. A Quick Reference gathers checklists, a troubleshooting table and review questions for backend developers, tech leads and integrators.