Nestjs Expert

---
name: nestjs-expert
description: Use when implementing nestjs functionality with production-grade patterns and safeguards.
metadata:
  hermes:
    tags: [codex-agent, backend-api]
    source: codex-field-kit/backend-api
---

# Nestjs Expert

## Focus Areas

- Dependency Injection (DI) and Inversion of Control (IoC) in NestJS
- Module organization and structure in large applications
- Middleware for logging, authentication, and request/response manipulation
- Exception filters for robust error handling
- Pipes for data transformation and validation
- Guards for authentication and route protection
- Interceptors for cross-cutting concerns like caching and logging
- Custom decorators for reusable components
- Integration and unit testing with Jest
- REST API design following NestJS conventions

## Approach

- Utilize NestJS's DI system to manage dependencies efficiently
- Break down applications into feature modules
- Implement global and scoped middleware for cross-cutting concerns
- Create custom exception filters for consistent error responses
- Use pipes to enforce data validation rules
- Design guards to handle complex authentication scenarios
- Leverage interceptors to handle common tasks like logging
- Write custom decorators to encapsulate repetitive patterns
- Ensure high test coverage with Jest
- Follow NestJS best practices for RESTful API design

## Quality Checklist

- Ensure all modules have clear separation of concerns
- Validate all incoming data with pipes
- Handle exceptions globally with an appropriate filter
- Maintain consistent logging throughout with middleware and interceptors
- Ensure all routes are protected with guards where necessary
- Write tests for all modules using Jest
- Use dependency injection to its fullest potential
- Follow DRY principles with custom decorators and utils
- Maintain clear and consistent API documentation
- Implement caching strategies using interceptors

## Output

- Efficient and scalable NestJS applications
- Well-organized modular structure
- Comprehensive test suite ensuring reliability
- Robust error handling with custom exception filters
- Secure endpoints with guards in place
- Reusable components through custom decorators
- Optimized performance with caching and logging
- Detailed API documentation generated using Swagger
- Consistent and maintainable codebase
- High-quality REST APIs following best practices