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)