What Is a Monorepo?

If you’ve spent any time in the world of software development, you’ve probably come across the term monorepo. Short for “monolithic repository,” a monorepo is a single version-controlled code repository that holds the code for multiple projects, services, or packages.

What Exactly Is a Monorepo?

A monorepo is a single repository that contains code for multiple projects that may or may not be related. This is in contrast to polyrepos, where each project lives in its own isolated repository.

For example, imagine a company that has a web frontend, a mobile app, and several backend services. In a monorepo setup, all of this code would live in the same Git repository, often organized in separate folders:

/apps
  /web
  /mobile
  /api
/libs
  /ui-components
  /auth

Each project or library can be developed independently but shares the same version control, issue tracking, and CI/CD workflows.

Benefits of a Monorepo

1. Single Source of Truth
   Everything is in one place, making it easier to understand the full picture and keep track of dependencies.

2. Atomic Changes
   Developers can make coordinated changes across multiple projects in a single commit, ensuring nothing breaks due to version mismatches.

3. Code Reuse
   Shared libraries and components can be easily imported and updated across projects.

4. Unified Tooling
   A single setup for linting, testing, and building makes development more consistent.

5. Simplified Dependency Management
   Versioning of internal packages can be simpler since all packages evolve together.

Challenges of a Monorepo

1. Scalability
   Very large repositories can slow down Git operations and CI pipelines if not properly managed.

2. Complex Permissions
   It can be harder to set up fine-grained access control for different teams or projects.

3. Tooling Requirements
   Monorepos often require specialized tools to manage builds, dependencies, and deployments efficiently.

Popular Monorepo Tools

• Nx: A powerful toolkit for monorepos with advanced support for dependency graphs, caching, and task running.
• Bazel: Developed by Google, it excels in managing large-scale codebases with a focus on performance.
• Lerna: Great for managing JavaScript/TypeScript projects with multiple packages.
• Turborepo: A high-performance monorepo build system optimized for modern web development.

Should You Use a Monorepo?

Monorepos can be a game-changer for teams that work on multiple related projects or want better integration between their codebases. However, they also come with their own complexities. If you’re running a small team or isolated services, a polyrepo might be more straightforward.

The decision largely depends on your team size, project structure, and long-term goals.