NestJS was deliberately designed so you can start simple and grow without rewriting. Here's how to take full advantage of that. When you start a new backend project, one of the first debates that comes up is: monolith or microservices? What are we actually talking about? Before comparing, let's align on definitions: Modular Monolith : a single application deployed as one unit, but with code organized into modules with clear boundaries. One module per business domain. Microservices : multiple independent applications that communicate over the network (HTTP, messaging, gRPC). Each service is deployed, scaled, and updated autonomously. The most common misconception is thinking "monolith" means "messy code." It doesn't. A monolith can be perfectly structured — and in NestJS, that's the norm, not the exception. Modular Monolith with NestJS NestJS was built for the modular monolith. Its module system forces you to think in terms of domains from day one.…