api-and-interface-design

To design backward-compatible REST API contracts, prefer additive, optional fields and safe extension patterns over breaking changes to existing types. This approach ensures predictable consumer integration and prevents accidental breakages when modifying public-facing type contracts across services.

Consistent error semantics across API endpoints require establishing a single error strategy, combining status-code mapping with a uniform structured error body. This ensures consumers receive predictable error behavior and clear contract definitions across all REST or GraphQL services.

Validate untrusted data at system edges, specifically user input, external service responses, and configuration, to establish safe frontend-backend boundaries. Avoid scattered validation that hides contract behavior, ensuring boundary-only validation protects internal module operations.

Define TypeScript interface patterns for stable module boundaries using discriminated unions and branded IDs to create predictable contracts. Contract-first specification ensures consumers and producers agree on typed inputs and outputs before implementation begins.

For REST resource pagination and partial updates, apply consistent naming conventions, standard pagination and filtering patterns, and PATCH partial update mechanisms. These stability conventions ensure interfaces remain predictable and difficult to misuse across endpoint designs.

Yes, contract-first interface design applies to both REST and GraphQL endpoint planning, defining typed inputs, outputs, and behavior before implementation. This ensures consumers and producers agree on the contract, reducing integration breakages across frontend-backend boundaries.