backend-development

Backend Development

Activate this skill when building backend services, APIs, or server-side logic.

When to Use

• Implementing REST or GraphQL API endpoints
• Building middleware (auth, logging, rate limiting, CORS)
• Designing service layer architecture
• Integrating with databases and external services
• Implementing background jobs and queues
• Setting up application configuration and environment management

Architecture Patterns

• Layered: Controller -> Service -> Repository
• Clean Architecture: separate domain from infrastructure
• CQRS: separate read and write models for complex domains
• Event-driven: pub/sub for decoupled services

Implementation Guidelines

• Validate all input at the boundary (controller/handler layer)
• Use dependency injection for testability
• Implement structured logging with correlation IDs
• Handle errors at appropriate layers (do not swallow exceptions)
• Use environment variables for configuration (12-factor app)
• Implement health check endpoints (/health, /ready)
• Use connection pooling for database connections
• Implement graceful shutdown handling

Error Handling

• Use typed error classes with error codes
• Return consistent error response format
• Log errors with context (request ID, user ID, operation)
• Never expose internal details in production error responses
• Implement global error handler as safety net

Testing Strategy

• Unit tests for service/business logic (no I/O)
• Integration tests for database and external service interactions
• API tests for endpoint behavior verification
• Load tests for performance-critical paths