How would you lazy-load a module in NestJS to improve startup time?
Use LazyModuleLoader (available since NestJS 8). Inject it and call load() with the module reference. The module and its providers are initialized on first call and then cached as a singleton. Useful for rarely-used heavy modules like PDF generation or image processing.
Lazy loading a module with LazyModuleLoader
Best use cases for lazy loading:
Heavy modules not needed at startup (PDF, image processing, report generators).
Rarely-invoked admin or background features.
Modules only needed for specific user roles or premium features.
Note: controllers cannot be lazy-loaded — only service-level providers.