Embracing Monorepos with Nest.js: A Scalable Approach for NE India's Backend Teams

What is a Monorepo and Why is it Useful for Backend Teams?

In the realm of backend development, a monorepo (short for "monolithic repository") has emerged as a preferred choice for teams managing multiple services or shared libraries. A monorepo consolidates all applications and libraries into a single repository, offering several benefits over traditional multi-repository setups.

• Shared code lives in one place: With a monorepo, developers can easily access and reuse common code across projects, reducing duplication and improving code consistency.
• Easier refactoring across projects: Changes made to shared libraries or utilities automatically affect all projects that depend on them, making it easier to maintain and update codebase.
• One set of tooling and configs: A monorepo simplifies the development process by providing a consistent environment for all projects, eliminating the need to manage separate toolchains and configurations.
• Simpler dependency management: Dependencies are managed at the repository level, making it easier to keep track of and manage shared dependencies across projects.

Nest.js Monorepo Support: An Official and Easy Approach

For Nest.js projects with microservices, background workers, or shared modules, a monorepo is an ideal choice. Nest.js offers first-class monorepo support via the Nest CLI, making it easy to create, manage, and scale your backend applications.

Setting Up a Nest.js Monorepo

To create a Nest.js monorepo, follow these steps:

1. Ensure the Nest CLI is installed: npm i -g @nestjs/cli
2. Create a monorepo workspace: nest new nest-monorepo
3. During setup, choose your preferred package manager (npm, yarn, or pnpm) and enable ESLint and Prettier if desired.
4. Enable monorepo mode by adding "monorepo": true to nest-cli.json
5. Generate your first app: nest generate app api
6. Create shared libraries: nest generate library common and nest generate library database

Importing Libraries into Apps

Libraries can be imported into apps using the auto-configured @app alias, making it easy to import shared modules without dealing with relative path issues.

Running Apps Independently

Each app can be run independently, with its own port, environment variables, and deployment options.

Building for Production

Apps can be built for production using the nest build command, with the option to build a specific app or all apps at once.

Best Practices for Nest.js Monorepos

• Keep libraries small: Libraries should solve one problem, and avoid dumping everything into a single common folder.
• Avoid circular dependencies: If two apps depend on each other, consider rethinking the design.
• Share DTOs and interfaces: This helps avoid duplication and keeps APIs consistent across projects.
• One database library: Centralize database logic instead of duplicating connections across projects.

When Not to Use a Monorepo

While monorepos offer numerous benefits, they may not be ideal for every situation. For example, if you have a single small service, fully independent teams, or significantly different deployment pipelines, a monorepo might not be the best choice.

Final Thoughts

Nest.js monorepos are an easy-to-set-up, officially supported, and scalable solution for growing backend systems. By embracing monorepos, you can enjoy clean boundaries, shared code, and fewer repositories to manage. Start small, add apps and libraries as your system grows, and maintain a simple and predictable structure for long-term success.