api-design-principles

REST API design centers on clear resource modeling, consistent HTTP method semantics (GET, POST, PUT, DELETE), and predictable URL structures. Structure endpoints around nouns (e.g., /products), use appropriate status codes, implement pagination for large datasets, and version your API to support changes without breaking existing clients.

Consistent error handling requires standardized response formats with meaningful error codes, human-readable messages, and appropriate HTTP status codes. Document error scenarios in your API specification, return structured error objects (not plain text), and include actionable information so clients can respond intelligently to failures.

REST excels for straightforward resource-based operations and mobile clients with bandwidth constraints; GraphQL suits complex, nested data queries and reduces over-fetching. Choose based on client needs: REST for simple, predictable access patterns; GraphQL when clients need flexible query control and you can manage schema-first development complexity.

Rate limiting protects API stability by restricting requests per client or user. Implement pagination to reduce payload size, use DataLoader patterns for efficient batch queries in GraphQL, add filtering capabilities so clients fetch only needed data, and document rate limits clearly so developers plan accordingly.

API versioning strategies include URL-based (/v1/, /v2/), header-based, or query-parameter approaches. URL versioning is most explicit and widely understood. Plan for backward compatibility, deprecate old versions gradually with clear timelines, and communicate changes in advance so dependent systems have time to migrate.

Effective API documentation includes clear endpoint descriptions, request/response examples, authentication requirements, error codes with solutions, and executable examples. Use tools that generate docs from specifications (OpenAPI/Swagger for REST, schema introspection for GraphQL), keep examples current, and explain the reasoning behind design decisions.