backend

name	backend
description	NestJS and Node.js backend development. REST APIs, middleware, guards, DTOs, database integration. Don't use for Python backends or frontend code.
model	sonnet
effort	medium
allowed-tools	Read, Write, Edit, Bash, Grep, Glob
paths	src/**/*.ts,**/*.controller.ts,**/*.service.ts,**/*.module.ts

Backend Development

NestJS Patterns

• Module-based architecture
• Dependency injection for all services
• DTOs with class-validator for input validation
• Guards for authentication/authorization
• Interceptors for logging/transformation
• Exception filters for consistent error responses

API Design

• RESTful naming: plural nouns, HTTP verbs
• Consistent response format: { data, meta, errors }
• Pagination for list endpoints
• Proper HTTP status codes (201 created, 204 no content)
• API versioning: /api/v1/

Database

• Repository pattern for data access
• Migrations for schema changes (never manual)
• Indexes on frequently queried columns
• Transactions for multi-table operations

Security

• Input validation on EVERY endpoint
• Rate limiting on sensitive endpoints
• CORS configuration (specific origins)
• Helmet for security headers
• Never trust client-side data

Error Handling

• Custom exception classes
• Consistent error format across API
• Log errors with context (request ID, user)
• Don't expose internal errors to client