Backend API

RESTful API design combines consistent route naming, proper HTTP methods, and secure authentication patterns. Implement token-based auth, validate all inputs, handle errors with standardized response codes, and version endpoints to enable safe integration across clients without breaking existing consumers.

Backend API authentication uses secure patterns like OAuth, JWT, or API keys to verify client identity, while authorization controls what authenticated clients can access. Enforce role-based access, never store secrets in code, use HTTPS exclusively, and validate permissions at every endpoint to prevent unauthorized data exposure.

Consistent error handling in APIs means returning standardized error response formats with meaningful status codes, validation messages, and request IDs for debugging. Document expected errors, validate input schemas before processing, and provide clear messages so frontend developers and API consumers can handle failures gracefully.

GraphQL and REST serve different query patterns: GraphQL lets clients request only needed fields from a single endpoint, while REST uses multiple fixed endpoints. Many backends expose both simultaneously, letting consumers choose based on their needs—REST for simple integrations, GraphQL for flexible, data-efficient queries.

API versioning through URL paths or headers prevents breaking changes when you update endpoints. Maintain clear documentation showing request/response formats, authentication requirements, error codes, and examples. Version incrementally and deprecate old versions gradually so existing integrations have time to migrate.

Test backend APIs by writing unit tests for individual endpoints, integration tests for authentication flows and error cases, and contract tests to verify client-server compatibility. Automate these tests in CI/CD pipelines, validate response schemas match documentation, and test edge cases like rate limiting and malformed requests.