NestJS best practices and architecture patterns for building production-ready applications. This skill should be used when writing, reviewing, or refactoring NestJS code to ensure proper patterns for modules, dependency injection, security, and performance.

NestJS Best Practices Comprehensive best practices guide for NestJS applications. Contains 40 rules across 10 categories, prioritized by impact to guide automated refactoring and code generation. When to Apply Reference these guidelines when: Writing new NestJS modules, controllers, or services Implementing authentication and authorization Reviewing code for architecture and security issues Refactoring existing NestJS codebases Optimizing performance or database queries Building microservices architectures Rule Categories by Priority Priority Category Impact Prefix 1 Architecture CRITICAL arch 2 Dependency Injection CRITICAL di 3 Error Handling HIGH error 4 Security HIGH security 5 Performance HIGH perf 6 Testing MEDIUM HIGH test 7 Database & ORM MEDIUM HIGH db 8 API Design MEDIUM api 9 Microservices MEDIUM micro 10 DevOps & Deployment LOW MEDIUM devops Quick Reference 1. Architecture (CRITICAL) arch avoid circular deps Avoid circular module dependencies arch feature modules Organize by feature, not technical layer arch module sharing Proper module exports/imports, avoid duplicate providers arch single responsibility Focused services over "god services" arch use repository pattern Abstract database logic for testability arch use events Event driven architecture for decoupling 2. Dependency Injection (CRITICAL) di avoid service locator Avoid service locator anti pattern di interface segregation Interface Segregation Principle (ISP) di liskov substitution Liskov Substitution Principle (LSP) di prefer constructor injection Constructor over property injection di scope awareness Understand singleton/request/transient scopes di use interfaces tokens Use injection tokens for interfaces 3. Error Handling (HIGH) error use exception filters Centralized exception handling error throw http exceptions Use NestJS HTTP exceptions error handle async errors Handle async errors properly 4. Security (HIGH) security auth jwt Secure JWT authentication security validate all input Validate with class validator security use guards Authentication and authorization guards security sanitize output Prevent XSS attacks security rate limiting Implement rate limiting 5. Performance (HIGH) perf async hooks Proper async lifecycle hooks perf use caching Implement caching strategies perf optimize database Optimize database queries perf lazy loading Lazy load modules for faster startup 6. Testing (MEDIUM HIGH) test use testing module Use NestJS testing utilities test e2e supertest E2E testing with Supertest test mock external services Mock external dependencies 7. Database & ORM (MEDIUM HIGH) db use transactions Transaction management db avoid n plus one Avoid N+1 query problems db use migrations Use migrations for schema changes 8. API Design (MEDIUM) api use dto serialization DTO and response serialization api use interceptors Cross cutting concerns api versioning API versioning strategies api use pipes Input transformation with pipes 9. Microservices (MEDIUM) micro use patterns Message and event patterns micro use health checks Health checks for orchestration micro use queues Background job processing 10. DevOps & Deployment (LOW MEDIUM) devops use config module Environment configuration devops use logging Structured logging devops graceful shutdown Zero downtime deployments How to Use Read individual rule files for detailed explanations and code examples: Each rule file contains: Brief explanation of why it matters Incorrect code example with explanation Correct code example with explanation Additional context and references Full Compiled Document For the complete guide with all rules expanded in a single document, see [AGENTS.md in the repository](https://github.com/Kadajett/agent nestjs skills/blob/main/AGENTS.md).

nestjs-best-practices