Monorepo vs Polyrepo - a comparison

When it comes to organising code repositories for software development projects, two popular approaches are monorepo and polyrepo. Both have their advantages and disadvantages, and choosing between them can have a significant impact on a project’s development and maintenance.

A monorepo, as the name suggests, is a single repository that contains all the code for a project. In contrast, a polyrepo is a set of repositories, each containing code for a specific part of the project.

Let’s take a closer look at the pros and cons of each approach.

Monorepo

Advantages

Centralised management

A monorepo provides a centralised location for all the code related to a project. This makes it easier to manage, since there is only one place to look for code, dependencies, and configurations.

Easier code sharing

With all the code in one repository, sharing code between different parts of the project becomes easier. This can lead to better code reuse and more consistent code across the project.

Better collaboration

Working in a monorepo can promote better collaboration between team members. Developers can see what others are working on and easily integrate changes into their own work.

Disadvantages

Complexity

A monorepo can become complex as the project grows, making it harder to navigate and maintain. It may also require more powerful tooling to manage the increased scale.

Higher risk

With all the code in one repository, there is a higher risk of a single issue causing problems across the entire project. This can make it harder to isolate and fix problems.

Slower builds

Since all the code is in one repository, building and testing the entire project can take longer than building and testing smaller, individual parts of the project.

Polyrepo

Advantages

Simplicity

Polyrepos are simpler to manage and navigate since each repository contains only the code related to a specific part of the project.

Isolation

Issues in one repository are less likely to affect other parts of the project, making it easier to isolate and fix problems.

Faster builds

Since each repository contains only a subset of the code, building and testing can be faster than in a monorepo.

Disadvantages

Dependency management

Managing dependencies across multiple repositories can be more challenging than in a monorepo. It can be harder to ensure that all the repositories are using the correct versions of shared dependencies.

Code sharing

Sharing code between repositories can be more difficult than in a monorepo, which can lead to more duplication of code.

Collaboration

Collaboration can be more challenging in a polyrepo since team members may not have visibility into what others are working on.

Conclusion

Deciding between a monorepo and polyrepo can depend on the size and complexity of the project, as well as the needs and preferences of the development team. A monorepo can be beneficial for larger projects with a lot of shared code and a need for centralised management, while a polyrepo may be more appropriate for smaller projects or those with more independent parts.

Ultimately, the choice between a monorepo and polyrepo will depend on a variety of factors, and both approaches can be effective when used appropriately.