One Pager Cheat Sheet

• This article discusses the differences between Monorepo and Polyrepo architectures for code repositories, highlighting that while Monorepos offer simplified dependency management and atomic changes, they can become difficult to manage due to their size, while Polyrepos provide isolation and speedy builds but can lead to dependency chaos and a high coordination overhead; the choice between them depends on various factors like team structure, project count, and release cadence.
• Monorepos provide several benefits for code development such as streamlined dependency management, enabling atomic changes, serving as a unified source of truth, offering simplified access control, and swift code search by centralizing all projects and their dependencies into one repository, thus enhancing efficiency, coordination, and security.
• Searching for code in a monorepo is not slower than in poly-repos due to the centralized, unified structure of a monorepo, allowing for a swift and comprehensive search, contrary to the need for potentially multiple searches across multiple repositories in a poly-repo setup.
• Monorepos have drawbacks including the Expanding Universe Problem, where the repository size grows exponentially slowing down operations; the Domino Effect, where a bug can affect multiple projects due to interdependent changes; the Access Control Puzzle, where fine-grained access control is hard to manage; and the CI Time-Trap, where Continuous Integration cycles become lengthy as the repository grows.
• The ease of dependency management is a strength of monorepos, where multiple projects co-exist in a shared repository allowing for direct referencing and eliminating the complexities of dependency drift, but the increased inter-project dependencies can heighten the risk of the Domino Effect, making it a potential challenge.
• Polyrepos offer a different paradigm for managing code, functioning like specialized shops that facilitate lean and focused repositories, granular access control, speedy CI/CD pipelines, an agile project lifecycle, and flexibility in code refactoring by keeping projects scoped, permissions managed at a granular level, only necessary code built and tested, microservices easily initiated and archived, and projects loosely coupled.
• The use of Polyrepo involves several challenges such as navigating dependencies, dealing with a fragmented source of truth, overcoming coordination issues, managing the overhead in repository management, and handling the duplication of tools and configurations, increasing complexity in the development process.
• A Polyrepo setup leads to a fragmented source of truth, making global operations like code search or policy implementation across the entire codebase more difficult and time-consuming compared to a centralized Monorepo setup.
• The choice between monorepos and polyrepos—which centralize or decentralize code respectively—depends on factors such as team structure, number of services, and release velocity, with no one-size-fits-all answer, and each having advantages and disadvantages suited to different scenarios.