4 min read - Building Scalable and Maintainable Systems with NestJS

In the world of backend development, the debate between monorepos and multi-repos has been a long-standing one. For years, the prevailing wisdom was to break down large applications into smaller, independent repositories (multi-repo). However, a growing number of teams are rediscovering the power of the monorepo, and for good reason. When combined with a modern framework like NestJS, a monorepo can be a powerful tool for building scalable and maintainable systems.

What is a Monorepo?

A monorepo is a single version control repository that holds the source code for multiple projects. These projects can be related—for example, a collection of microservices that make up a larger application—or they can be completely independent.

This approach has been used for years by tech giants like Google, Facebook, and Microsoft, but it's now becoming increasingly accessible to teams of all sizes, thanks to modern tooling like Nx and Turborepo.

The Monorepo Advantage with NestJS

NestJS, with its modular architecture and built-in support for building microservices, is a natural fit for a monorepo. Here's why this combination is so powerful:

1. Simplified Dependency Management: In a multi-repo setup, managing dependencies across multiple projects can be a nightmare. Different services can end up with different versions of the same library, leading to inconsistencies and bugs. In a monorepo, all projects share a single node_modules folder, ensuring that everyone is using the same version of every dependency.

2. Atomic Commits and Cross-Project Refactoring: One of the biggest advantages of a monorepo is the ability to make atomic changes across multiple projects in a single commit. Need to update a shared library and all the services that use it? In a monorepo, that's a single, atomic operation. This makes large-scale refactoring much safer and easier to manage.

3. Seamless Code Sharing: With a monorepo, sharing code between projects is trivial. You can easily create shared libraries for things like authentication, logging, or data models, and then import them into any of your services. This promotes code reuse and helps to ensure consistency across your entire system.

4. Unified Tooling and CI/CD: A monorepo allows you to have a single, unified set of tools for linting, testing, and building all of your projects. This simplifies your CI/CD pipeline and ensures that all of your code adheres to the same quality standards. Modern monorepo tools can even intelligently figure out which projects have been affected by a change and only run tests for those specific projects, saving valuable time.

Getting Started with NestJS and Monorepos

The NestJS CLI has built-in support for creating and managing monorepo projects. With a few simple commands, you can create a new monorepo, add applications (e.g., microservices), and create shared libraries.

When you combine this with a tool like Nx, you get even more powerful features, such as computation caching (which can dramatically speed up your builds) and dependency graph visualization.

Is a Monorepo Right for You?

While monorepos offer many advantages, they're not a silver bullet. They can introduce their own set of challenges, such as the need for more sophisticated CI/CD pipelines and the potential for longer build times if not managed properly.

However, for teams building complex, multi-service applications with NestJS, the benefits of a monorepo often outweigh the drawbacks. By centralizing your code and tooling, you can create a more streamlined, efficient, and collaborative development environment.

At Exceev, we've helped numerous clients make the switch to a monorepo architecture, and the results speak for themselves: faster development cycles, higher code quality, and a more maintainable system. The rise of the monorepo is here to stay, and it's time to see if it's the right fit for your next NestJS project.