api-and-interface-design

Contract-first API design means defining the interface specification before implementation. Use it for REST, GraphQL, or module boundaries to enforce stable data sharing and prevent fragile integrations between frontend and backend teams.

To design hard-to-misuse REST APIs, enforce consistent error semantics, validate external input at boundaries, and use clear naming conventions. Extend interfaces with new optional fields rather than modifying existing ones to avoid breaking consumers.

The best way to handle API error handling consistently is to choose one error strategy and apply it uniformly across all endpoints. This prevents confusion and ensures predictable behavior across REST, GraphQL, and module boundaries.

Validate external input at API boundaries to prevent internal assumptions from breaking. This contract-first approach ensures external data conforms to the interface spec before reaching internal module logic or downstream processing.

Yes, contract-first design works for REST and GraphQL interfaces, as well as any public boundary where teams share data or components. It enforces additive changes, consistent naming, and boundary validation across endpoints.

Prefer addition over modification when changing module contracts to avoid breaking existing consumers. Extending interfaces with new optional fields maintains backward compatibility while allowing the API surface to grow safely.