What is a feature module in NestJS and why should you use them instead of putting everything in AppModule?
A feature module groups all the code for a single domain — its controllers, services, repositories, and DTOs — into one cohesive unit. AppModule only imports feature modules rather than declaring every provider itself. This improves navigation, independent testability, clear ownership, and enables lazy loading.
Feature module pattern
Benefits of feature modules:
Single responsibility — each module owns one domain and nothing else.
Independent testability — feature modules can be tested in isolation with a TestingModule.
Clear ownership — team members know exactly where code for a domain lives.
Lazy loading — heavy feature modules can be loaded on demand without touching AppModule.
AppModule stays small — acts only as the composition root, not a dumping ground.