Monorepo vs Polyrepo: Which Strategy Should You Choose?

When working on complex software projects, the choice between monorepo and polyrepo can significantly impact your team's productivity and code scalability. In this article, we analyze the differences, pros and cons of each approach, and help you understand which one is right for you.

What are Monorepo and Polyrepo?

Monorepo

A monorepo (monolithic repository) is a single repository that contains the source code for multiple projects, services, or packages, often related to each other.

my-monorepo/
  packages/
    frontend/
    backend/
    shared/
  package.json
  turbo.json

Polyrepo

A polyrepo (multiple repositories) means that each project, service, or package has its own separate repository.

repos/
  frontend/
    package.json
  backend/
    package.json
  shared/
    package.json

Visual Difference

Pros and Cons

Monorepo

Advantages:

• Makes code sharing easier (e.g., shared libraries).
• Atomic refactoring across multiple projects.
• Centralized management of dependencies and configurations.

Disadvantages:

• Can become heavy as codebase grows.
• Requires tools to manage partial builds/tests (e.g., Nx, Turborepo).

Polyrepo

Advantages:

• Each team/project is independent.
• Easier to manage for small projects.
• Allows for granular access policies.

Disadvantages:

• Harder to share code without publishing packages.
• Cross-repo refactoring is more complex.
• Possible duplication of configurations.

Practical Example: Monorepo with Turborepo

Suppose you want to create a monorepo with frontend and backend using Turborepo.

1. Initialize the monorepo

npx create-turbo@latest

2. Typical structure

my-monorepo/
  apps/
    web/        # frontend Next.js
    api/        # backend Node.js/Express
  packages/
    ui/         # shared component library
    utils/      # shared functions
  turbo.json
  package.json

3. Example workspace in package.json

{
  "private": true,
  "workspaces": [
    "apps/*",
    "packages/*"
  ]
}

4. Example of importing a shared library

Suppose you have a function in packages/utils/src/formatDate.ts:

// packages/utils/src/formatDate.ts
export function formatDate(date: Date): string {
  return date.toLocaleDateString('en-US');
}

In the frontend:

// apps/web/pages/index.tsx
import { formatDate } from '@myorg/utils';

export default function Home() {
  return <div>Today is {formatDate(new Date())}</div>;
}

When to Choose Monorepo?

• Medium-large teams working on multiple related projects.
• Need to share code and perform large-scale refactoring.
• Projects that grow quickly and require optimized builds/tests.

When to Choose Polyrepo?

• Small or independent projects.
• Separate teams working on different products.
• Very restrictive access policies.

Conclusion

There is no perfect solution for everyone. The choice depends on team size, project complexity, and collaboration needs. The important thing is to be aware of the trade-offs and choose the right tools to manage complexity.