Monorepo Vs Polyrepo Architecture: A Comparison For Effective Software Development

Julian Wallis
20 min read
Buildings facing each other

Are you confused about whether to use Monorepo or Polyrepo architecture for your next software development project? You’re not alone. The debate over the two architectures has been raging for years. While both architectures have their own set of advantages and disadvantages, choosing the right one depends on several factors, including the size of your team, the complexity of your project, and your development goals.

Whether you’re a software developer, a project manager, or a technology enthusiast, this blog article will provide you with the knowledge and insights you need to understand the battle between Monorepo and Polyrepo architectures.

Before we dive into choosing Monorepo vs Polyrepo architecture, let’s first understand what they are and how they work.

What Is Monorepo Architecture? 🏛️

Monorepo architecture, also known as a “single repository” or “mono-repository,” is an approach to software development where all of the code for a project or organisation is stored in a single repository. This is in contrast to a Polyrepo architecture, where each project or component has its separate repository.

The idea of a Monorepo is not new, and large software organisations have used it for many years. Some of the earliest examples of Monorepo architecture can be traced back to the early days of software development when the only option for storing code was a mainframe computer. As the technology evolved, distributed version control systems like Git and Mercurial made it easier for developers to work with Monorepos, and many large software organisations began adopting the approach.

Smaller organisations can also benefit from using a Monorepo, especially if they have multiple projects or components that share common codes or dependencies. Storing all of the code in a single repository can simplify development and testing workflows, reduce the risk of code duplication or fragmentation, and make it easier to manage versioning and releases.

However, Monorepo architecture is not without its challenges. Managing a large Monorepo can be complex, especially when it comes to maintaining a clean and consistent codebase, dealing with conflicts and merge issues, and managing access controls and permissions. Additionally, because all of the code is stored in a single repository, a mistake or issue with one component can potentially impact the entire codebase.

Despite these challenges, Monorepo architecture continues to be a popular approach to software development, especially in larger organisations. Many open-source projects also use Monorepo architecture, including Facebook’s React project, which stores all of the code for the React library and related tools in a single repository.

Pros Of Monorepo Architecture 🎖️

👨‍💻 Easier Code Management

With all code stored in one central location, developers can easily access and manage code without the need for complex branching and merging strategies. This can save time and reduce the risk of errors that can occur when managing multiple repositories.

Moreover, Monorepo architecture can simplify tasks such as code review, documentation, and version control. Developers can easily track changes and see how different parts of the codebase are connected, improving code quality and reducing the risk of conflicts.

♻️ Better Code Sharing & Reuse

Monorepo architecture has the ability to easily share and reuse code across different projects. By having all code in one central repository, developers can quickly access and reuse components that have already been created without having to duplicate efforts or reinvent the wheel. This can lead to faster development cycles, better collaboration, and improved code quality.

Additionally, Monorepo architecture can help reduce the amount of code duplication and inconsistency that can occur with Polyrepo architecture, as all code is stored in one place and can be easily managed and updated.

👁️ Improved Visibility

With all code stored in a single repository, developers have better visibility into the entire codebase. They can easily track changes, understand how different parts of the codebase are connected, and identify potential issues. This improved visibility can lead to better collaboration, as developers can more easily understand how their changes affect the rest of the codebase. It can also improve code quality, as developers can identify and address issues more quickly.

Additionally, better visibility can help reduce the risk of conflicts that can arise when multiple repositories are used, as all changes are made in the same location.

🧪 Simplified Testing & Deployment

With all code stored in one centralised location, testing and deploying changes becomes easier and more streamlined. Since there’s only one repository, there’s no need to manage dependencies across multiple repositories or worry about inconsistencies between different versions of code. This simplifies the QA testing and deployment process, reduces the risk of errors, and saves time. In addition, it can also improve the speed and efficiency of Continuous Integration and Continuous Deployment (CI/CD) pipelines, which can further improve the development process.

Overall, Simplified Testing and Deployment is a compelling reason to consider using Monorepo architecture in software development.

🤝 Improved Collaboration

With Monorepo, all developers have access to the same codebase, which allows them to work on different parts of the project simultaneously. This can lead to faster development cycles and better coordination among team members. By having a single repository for all code, Monorepo architecture also encourages developers to collaborate more effectively. They can share code easily, discuss issues, and track changes to the codebase in real time. This leads to better communication and collaboration within the team, which can help to improve the quality of the final product.

Monorepo vs Polyrepo: Improved team collaboration

Moreover, improved collaboration can also lead to better knowledge sharing and a more cohesive team. Developers can learn from each other, share their expertise, and develop a better understanding of the project as a whole. This can lead to a stronger team dynamic and a more effective development process.

Cons Of Monorepo Architecture

⛰️ Large Codebases

As the codebase grows, it can become difficult to manage and slow down the development process. This is because managing a large codebase can require significant time and resources to keep it organised and maintainable.

Additionally, large codebases can increase build times, making it more challenging to test and deploy changes quickly. To mitigate these issues, developers using Monorepo architecture need to establish clear guidelines and best practices for managing large codebases, such as breaking the codebase into smaller modules or using code reviews to ensure that changes are thoroughly tested and do not introduce unexpected consequences.

🤹 Need For More Coordination

Because all code is stored in a single repository, changes made to one part of the codebase can affect others. This can lead to unexpected consequences and require more coordination and testing to ensure that changes do not cause conflicts or break other parts of the codebase. The need for increased coordination can slow down development cycles and reduce overall productivity. To mitigate this risk, clear guidelines and best practices should be established for collaboration within the team.

🧷 Single Point Of Failure

Since all the code is stored in a single repository, if the central repository goes down, it can bring the entire development process to a halt. This can lead to a significant impact on the project, and developers may not be able to access the codebase until the repository is back up and running. This can be a risk for projects that rely on Monorepo architecture, and it is essential to have a robust backup plan to minimise the impact of such a situation.

🚧 Limited Flexibility

If a project requires the use of multiple languages or frameworks, Monorepo architecture may not be the best choice. In this scenario, a Polyrepo architecture would allow for more flexibility by separating the code into different repositories, each using the appropriate language or framework. While it’s possible to use multiple languages or frameworks in a Monorepo, it can increase the complexity of the codebase and make it harder to maintain over time.

🧬 Increased Complexity

As the codebase grows, the complexity of the Monorepo architecture can increase, making it more difficult to maintain and manage over time. This complexity can lead to longer build times, slower development cycles, and more challenging debugging and testing processes. Additionally, it can become difficult to track dependencies and maintain code quality, which can lead to conflicts and errors in the codebase. To mitigate this, developers must implement robust strategies for managing and organising the codebase, such as modularisation and automated testing.

What Is Polyrepo Architecture? 🏰

Polyrepo architecture is a software development approach where each project or component is stored in a separate repository. This is in contrast to Monorepo architecture, where all the source code for a project or a group of related projects is stored in a single repository. Polyrepo architecture has been the traditional approach to software development, and it is still used by many companies today.

The history of Polyrepo architecture can be traced back to the early days of software development when version control systems were first introduced. At that time, there was no concept of separate repositories for different projects or components, and all code was stored in a single repository. However, as software development became more complex and teams became larger and more distributed, the concept of separate repositories for different projects or components emerged.

In the early days of software development, the most common version control system was CVS (Concurrent Versions System). CVS was a centralised system where all code was stored on a single server, and developers would check out code, make changes, and then check it back in. With the emergence of newer technology in distributed version control systems, such as Git and Mercurial, it became easier to work with multiple repositories.

This means that teams can work independently and deploy changes to their services more quickly without worrying about breaking other parts of the system. However, it leads to difficulty in maintaining consistency between services. With each service having its repository, it can be challenging to ensure that all services are using the same libraries and dependencies. This can lead to duplication of code and inconsistencies in the system.

Now, you might be wondering which architecture is better suited for your project. Well, the answer is not straightforward and depends on a variety of factors. For example, Monorepo architecture works well for large teams working on complex projects with interdependent code, while Polyrepo architecture is better suited for smaller teams working on simpler projects that can be developed and deployed independently.

Pros Of Polyrepo Architecture 🎖️

🤸‍♂️ Flexibility

Polyrepo architecture offers greater flexibility compared to Monorepo architecture. Since each project has its own repository, it is easier to work with different programming languages or frameworks without having to worry about conflicts. Developers can choose the tools and technologies that best suit their project’s specific needs without being limited by the Monorepo structure.

Additionally, each repository can have its own release cycle, allowing for greater flexibility in deploying updates and changes. Overall, Polyrepo architecture can provide more flexibility and customisation options for development teams.

👨‍👦‍👦 Easier Management For Smaller Teams

One advantage of Polyrepo architecture is that it can be easier to manage smaller teams. With Polyrepo, each repository can be dedicated to a specific project or component, which can simplify code management and reduce the risk of conflicts. Smaller teams may find this approach more manageable and efficient, as they can focus on specific projects without having to navigate a large, centralised codebase.

Additionally, with smaller repositories, developers may have an easier time reviewing code, tracking changes, and coordinating with others.

👤 Improved Isolation

In a Polyrepo setup, each project or component is stored in a separate repository, which means that they are isolated from one another. This can be especially useful for larger or more complex projects, where it may be necessary to isolate certain components or applications to prevent dependencies or conflicts. Improved isolation also makes it easier to manage different versions of a component, as each version can be stored in its own repository.

Additionally, Polyrepo architecture allows for more flexibility in terms of programming languages and frameworks, since each repository can be configured to work with the specific tools and technologies required for that project or component.

🎟️ More Straightforward Version Control

With Polyrepo, each project has its own repository, making it easier to track changes and version control. This can be particularly beneficial for larger teams or projects with multiple contributors. Each repository can be managed independently, allowing for more granular control over changes and versioning.

Monorepo vs Polyrepo: Better version control

Additionally, since each repository is smaller in size, it can be easier to manage and maintain, reducing the risk of errors or conflicts in the version control process. This can lead to a more streamlined development process and faster time-to-market.

📈 Improved Performance

Polyrepo architecture can offer improved performance, particularly in large-scale projects. With code stored in separate repositories, it can be easier to manage and distribute resources, which can lead to faster build and deployment times. Additionally, because each repository can be managed independently, it may be possible to optimise code and dependencies for each specific project or module, further improving performance. This can be especially important for projects with high traffic or strict performance requirements.

Cons Of Polyrepo Architecture

🙅‍♀️ Limited Code Sharing

Since each project has its own repository, it can be challenging to share code between projects. This can lead to duplicated code and a lack of consistency in dependencies, which can increase the risk of errors and make it more difficult to maintain the codebase over time. In addition, sharing code between repositories can require additional setup and configuration, which can add to the development time and complexity.

However, this limitation can be mitigated by implementing effective dependency management and establishing clear guidelines for code sharing and reuse.

🔀 Increased Complexity

In a Polyrepo setup, code is distributed across multiple repositories, which can lead to increased complexity in terms of code management, testing, and deployment. Developers may need to manage dependencies between multiple repositories, which can become more challenging as the number of repositories increases.

Additionally, if different teams are responsible for different repositories, coordinating changes and ensuring consistency across the entire codebase can become more difficult. This can make it harder to maintain and manage the codebase over time, especially as the project grows in size and complexity.

🤼 Demand For Better Coordination

With separate repositories for different projects, it can be difficult to ensure that changes made in one repository do not negatively impact others. Changes made to one repository may have unforeseen effects on another, requiring additional testing and coordination between teams. This can be particularly difficult when dealing with large projects that involve multiple teams working on different parts of the codebase.

Without proper coordination and communication, it is possible for conflicts and inconsistencies to arise, leading to delays and additional work for developers. To mitigate these challenges, it is important for teams using Polyrepo architecture to establish clear guidelines and processes for coordinating changes across multiple repositories.

⚔️ Risk Of Dependency Conflicts

In a Polyrepo architecture, each repository may have its own dependencies, which can lead to different versions of the same library being used across repositories. This can result in compatibility issues and make it difficult to maintain and update the dependencies. As a result, developers may need to spend more time resolving conflicts and ensuring compatibility, which can slow down the development process and increase the risk of errors.

Additionally, these conflicts can make it harder to ensure a consistent user experience across different parts of the application.

Higher Overhead

Because the code is distributed across multiple repositories, it can be more time-consuming to manage and maintain. Each repository may require separate testing, deployment, and version control processes, which can add to the overall overhead. Additionally, the need to manage multiple repositories can lead to more administrative tasks such as access control, user management, and backup and recovery. This increased overhead can make Polyrepo architecture more complex and difficult to manage, especially for larger projects with many repositories.

Monorepo vs Polyrepo: Man having trouble with software

Which To Choose: Monorepo Vs Polyrepo ⚔️

Choosing either of the architectures influences your outcome to a greater extent. And, to say one is better than the other can be misleading to various degrees; therefore, let’s focus on the most popular use cases and characteristics to determine which architecture suits your interest.

  • Ease Of Importing: In comparing Monorepo vs Polyrepo architectures, Monorepo holds an advantage in code importing. With all code centralised in one repository, accessing and importing from different sections of the codebase becomes effortless. Conversely, Polyrepo architecture might present challenges in importing code from various repositories, mainly when managed by different teams or organisations.
  • Ease Of Contributing Within & Across Projects: Polyrepo architecture offers flexibility for contributions across different projects, as each repository can host its contributors and maintainers. On the other hand, Monorepo architecture tends to be more restrictive since all contributors require access to the same repository. Nevertheless, adequate access controls and team structures can enable collaboration across projects within a Monorepo setup.
  • Viewing Differences: When considering Monorepo vs Polyrepo architecture, Monorepo shines in simplifying viewing differences between code versions since all changes reside in one location. Comparatively, Polyrepo architecture makes tracking code differences more challenging, especially when changes span multiple repositories.
  • Structure Of Releases: Polyrepo allows more freedom in managing releases, as each repository can follow its release schedule and versioning system. In contrast, Monorepo architecture demands coordinated releases across the entire codebase, posing a more intricate challenge.
  • Builds & CI: Monorepo architecture streamlines builds and continuous integration (CI) processes, facilitating easier testing and integration of changes into the broader system. In contrast, Polyrepo architecture introduces complexity in managing builds and CI across multiple repositories.
  • Open Vs Closed Source: In the ongoing debate of Monorepo vs Polyrepo architectures, Polyrepo architecture is commonly favoured in open-source projects, where different entities manage diverse sections of the codebase. Conversely, Monorepo architecture finds prevalence in closed-source projects where a single organisation oversees the entire code.
  • Issue Tracking: Monorepo architecture simplifies issue tracking by centralising all the code-related problems in one location. In contrast, Polyrepo architecture poses challenges in issue tracking, particularly when issues are scattered across multiple repositories.

To sum up, the Monorepo approach streamlines code management and collaboration within a centralised repository, simplifying tasks like importing, viewing differences, and issue tracking. Conversely, Polyrepo architectures offer flexibility across diverse projects and release management but introduce complexities in code integration and tracking across multiple repositories. 

At the end of the day, the choice between the two hinges on your project’s scale, collaboration needs, and management preferences.

Hybrid Repository Strategies 🤝

Creating a hybrid repository model blends the advantages of Monorepo and Polyrepo, offering a middle ground for streamlined collaboration and efficient builds. This approach involves structuring repositories around teams or platforms – enabling the sharing of common code among services without the concern of disrupting others’ pipelines. With careful management to prevent it from becoming a full-fledged Monorepo, you can mitigate CI drawbacks and potentially eliminate the need for build-time optimisation tools.

While a hybrid approach might incur slightly longer build times compared to a Polyrepo setup, the trade-off between implementing additional build tools and actual build duration may not justify the added cost. Striking a balance between build efficiency and repository structure becomes pivotal in optimising development workflows.

Implementing Monorepo & Polyrepo Architecture 👷

Here are some practices to help you successfully implement Monorepo or Polyrepo architecture and ensure that your codebase remains consistent, maintainable, and scalable over time.

🗳️ 1. Choose The Right Version Control System

  • Ensure your version control system can handle the scale of your codebase and the number of developers working on it.
  • Use features like branching and merging to facilitate code sharing and collaboration.
  • Consider tools like Git submodules or Git subtrees to manage dependencies and submodules within a Monorepo architecture.

🛠️ 2. Use Automation Tools To Manage The Implementation

  • Use automated testing frameworks to ensure that code changes don’t have unintended consequences.
  • Use continuous integration (CI) and continuous delivery (CD) pipelines to automate the process of building, testing, and deploying code changes.
  • Use containerisation to ensure that the development environment is consistent across all developers and deployment environments.

📐 3. Establish Clear Guidelines & Standards For Code Sharing & Dependency Management

  • Define clear boundaries between code modules or services to avoid unnecessary coupling.
  • Establish guidelines for how code should be shared between modules or services.
  • Use package managers to manage dependencies and ensure that the correct versions of dependencies are used.

🖇️ 4. Implement A CI/CD Pipeline

  • Use a CI/CD pipeline to automate the process of building, testing, and deploying code changes.
  • Ensure that the pipeline includes quality checks like code linting, unit testing, and integration testing.
  • Use a version control system to track changes and ensure that only approved changes are deployed to production.

🕵️ 5. Regularly Review & Refactor The Codebase

  • Schedule regular code reviews to ensure that code quality standards are being met and to identify potential issues or inefficiencies in the codebase.
  • Refactor the codebase as needed to ensure that it remains maintainable and scalable.
  • Use code analysis tools to identify potential technical debt and prioritise refactoring efforts accordingly.

Companies Using Monorepo Architecture 🏢

🔎 Google

Google logo

Google is perhaps the most well-known example of a company that uses Monorepo architecture. Their codebase is managed in a single repository, which allows for easy collaboration across teams and projects. This approach has enabled Google to scale its development efforts and release new features and products quickly.

📞 Whatsapp

Whatsapp logo

WhatsApp, as a part of Facebook’s development ecosystem, uses a monorepo architecture for its software development. Facebook, the parent company of WhatsApp, has implemented a monorepo called “Buck” to manage its extensive codebase, which includes various projects like Facebook, Instagram, and WhatsApp.

🛏️ Airbnb

Airbnb logo

Airbnb employs a monorepo architecture to manage its codebase. It allows them to share code and libraries across different services and projects, providing a consistent development experience and facilitating code reuse. It also helps the company maintain consistency and reduce duplication of efforts.

Companies Using Polyrepo Architecture 🏘️

🛒 Amazon

Amazon logo

Amazon, on the other hand, uses Polyrepo architecture to manage its codebase. They have separate repositories for each of their services, which allows for more flexibility in terms of development and release management. This approach has also allowed Amazon to scale its development efforts and release new products quickly.

🚗 Tesla

Tesla logo

Tesla uses a polyrepo architecture in its software development process. By leveraging polyrepo architecture, Tesla can efficiently manage its software codebase, facilitate collaboration among development teams, and deploy updates to different components of its vehicles and infrastructure. It also helps maintain agility and scalability.

🚖 Uber

Uber logo

Uber is another example of a company that uses Polyrepo architecture to manage its codebase. They have separate repositories for each of their services, which allows for more flexibility in terms of development and release management. This approach has also allowed Uber to scale their development efforts and release new products quickly.

Final Words: Monorepo Vs Polyrepo Architecture 🏁

Looking to make the right call on whether to go with a Monorepo or Polyrepo architecture for your next software development project comes down to various factors, such as the size of your team, the complexity of your project, and your deployment requirements.

On the one hand, a Monorepo architecture can offer benefits such as improved code sharing and simpler dependency management, but it can also cause slower build times and increased complexity in code review and testing. On the other hand, a Polyrepo architecture can offer greater flexibility and faster build times, but at the cost of potential issues such as code duplication and inconsistent dependencies.

Whichever option you choose, it’s crucial to carefully consider your project’s specific needs and goals. Establishing clear guidelines and best practices can help ensure effective collaboration within your team. By weighing up the pros and cons of each approach, you’ll be able to make an informed decision that fits your project and team dynamics like a glove.

If you have any other questions about the monorepo and polyrepo architectures, feel free to reach out to us for a friendly discovery chat.

Published On

May 31, 2023