pact-backend-patterns

Error handling in backend APIs uses structured, consistent error taxonomy with standardized response formats. This Skill provides patterns for categorizing errors, mapping them to HTTP status codes, and returning actionable error messages that clients can parse and act on reliably.

Service layer patterns encapsulate business logic and orchestrate dependencies separately from HTTP concerns. This approach isolates domain logic, makes testing easier, and allows the same business rules to serve multiple endpoints or protocols like REST and GraphQL.

Layered validation combines schema validation at the HTTP boundary with business-rule validation in the service layer. This Skill covers implementing both approaches so invalid data fails fast at the API level while complex rules are enforced where they belong in business logic.

Yes. Middleware patterns abstract cross-cutting concerns like authentication, logging, and request preprocessing. This Skill applies middleware guidance to both REST and GraphQL APIs, allowing you to standardize security and validation logic across protocol types.

The repository pattern abstracts data access behind a contract, decoupling business logic from database implementation details. Use it to enable testing, support multiple data sources, and make schema changes without affecting service layer code.

This Skill provides an API implementation checklist covering controller patterns, request validation, error responses, and authentication boundaries. Follow it to ensure endpoints handle edge cases, reject invalid input, and communicate failures clearly to clients.