Streamlining Codebases: How Google and Tech Giants Master MonoRepo Maintenance

Any modern software service means it will change every day even every hour therefore the code base of the software company should be agile and simple enough to adapt the changes as quickly as it can. Over the past decade, many companies have shifted to using a single codebase which is commonly known as a monorepo (monolithic repository).

In this article, we will explore why major tech companies are adopting this approach instead of the multi-repo model, which was more popular before the 2000s. This article will explore the benefits, challenges, and alternative approaches companies can use to handle their codebases effectively.

What Is a Monolithic Repository?

A repository is the storage location for a company’s codebase. In software development, source code is the backbone of modern software and needs to be stored somewhere for version control, updates, and collaboration. This central storage system serves as the foundation for building software applications.

In large companies like Google, Meta, Uber, and Airbnb, thousands of engineers work on codebases daily. Bugs are found, changes are made, and software upgrades occur continuously. To manage all of this, companies require a storage system that can handle code, documentation, shared folders, and other types of files efficiently.

Based on the structure and operation of a repository, we can categorize it into three main types:

• Multi-repository (multi-repo): Components of a software project are stored in separate Git repositories.
• Monolithic repository (monorepo): Everything is stored in a single repository.
• Hybrid: Some components are stored in a monolithic architecture, while others are stored in a multi-repo format.

Interestingly, many tech giants are now adopting monolithic architectures, despite the challenges involved, due to the significant advantages they offer.

Benefits of Monorepos

• Simplified Code Management: Managing a centralized codebase is much easier compared to multiple repositories. It simplifies tracking changes, applying upgrades, and finding bugs. Since all the information is stored in one place, duplication risks are reduced, and version control strategies become more streamlined.
• Better Collaboration: Monorepos enables developers to share their code reviews and communicate with their teams seamlessly. This unified repository fosters better collaboration, as all components are stored in one location. It eliminates the need for extensive inter-team communication and ensures that everyone is working with the same information.
• Unified Version Control: In a multi-repo setup, separate repositories need to be updated simultaneously to ensure that the entire development process remains functional. In a monorepo, all projects can be versioned together, which simplifies dependency management. When an upgrade occurs, all dependencies are updated simultaneously.
• Atomic Changes: For large-scale operations across multiple projects, atomic changes are a critical advantage. Monorepos ensures that changes can be applied consistently across the codebase, reducing integration issues. This is especially beneficial for companies like Google and Meta, where seamless automation is essential.

Challenges of Monorepos

Despite their many benefits, monorepos come with significant challenges, both technical and cultural:

• Maintenance Complexity: Maintaining a single, large repository requires considerable investment in time, resources, and expertise. For smaller companies, the effort and cost may outweigh the benefits.
• Resource Consumption: Managing a monorepo can consume more resources than the actual software development process. The time spent maintaining the architecture can delay the overall development timeline.
• Security Risks: Since all data is stored in one location, a failure or security breach in the repository can disrupt the entire operation. This makes robust access control and security measures critical for effective monorepo management.
• Cultural Challenges: Specific cultural values like continuous learning, innovation, cross-functional teamwork, and open communication are required for the implementation. Without these cultural foundations, implementing and maintaining a monorepo effectively is difficult.

How Google Succeeds with Its Monorepo

For a company managing over 271 products, large-scale refactoring is essential. Google’s custom-built system for hosting its monolithic repository is called Piper. Here’s how Google leverages monorepos successfully:

• Piper: Piper ensures that Google’s global infrastructure is standardized and replicable. It operates with caching and asynchronous processes to maintain smooth operations for software developers worldwide. Developers interact with Piper using Clients in the Cloud (CitC), which allows them to use standard UNIX tools for code browsing and building.
  With a single repository, Google achieves a Single Source of Truth, eliminating the issue of conflicting file versions. Developers can browse and edit files across the repository from their dedicated workspaces using CitC.
• Bazel: Google also developed Bazel, an open-source build tool. Bazel accelerates the development process by caching build results and rebuilding only the necessary parts of the codebase. It supports multiple programming languages such as Java, C++, C#, Go, and Python, making it versatile across different language stacks.
• Continuous Integration/Continuous Deployment (CI/CD): Google uses an advanced CI/CD pipeline to ensure that the codebase remains functional. Code changes are automatically deployed after passing rigorous tests, minimizing the risk of errors.
• Dependency Management: Google’s single dependency version model ensures that all projects reference the same versions of libraries and tools. Their custom-built Code Search Tools simplify the process of finding and modifying code efficiently. Access control measures prevent unauthorized access to sensitive code, ensuring security.

Monorepo Strategies at Other Companies

• Meta: Meta also employs a monorepo strategy to enhance internal collaboration and streamline development. Their unified code access allows developers to access most of the company’s codebase, fostering productivity by enabling teams to resolve dependency issues independently.

• Airbnb: Airbnb’s adoption of a monorepo strategy centers around improving developer efficiency and collaboration. By consolidating codebases into a single repository, Airbnb enhances code visibility and sharing among teams. This approach not only reduces the complexities associated with dependency management but also accelerates the development process, enabling rapid iteration and continuous integration.

• X (formerly Twitter): X uses monorepo strategy to streamline its development workflows and ensure consistency across its vast codebase. The unified repository allows for seamless cross-team collaboration and simplifies the integration of new features and updates. By maintaining a single source of truth for their code, X reduces technical debt and enhances the scalability and maintainability of their platform.

In conclusion, while monorepos offer several benefits—such as simplified code management, better collaboration, unified version control, and atomic changes—they also come with challenges like maintenance complexity, resource consumption, and cultural adaptation. For large tech companies like Google and Meta, the advantages often outweigh the challenges, making monorepos an effective choice. However, smaller companies may need to weigh the costs and benefits before adopting this approach.