Brief Introduction
In software development, how code repositories are structured plays a critical role in collaboration, efficiency, and scalability. Two primary approaches are Mono-repo (monolithic repository) and Multi-repo (multiple repositories). Each approach has distinct advantages and challenges, depending on the needs of the organization, the team size, the complexity of the projects, and the tools in use.
- Mono-repo: In a mono-repo, all codebases, modules, libraries, and even microservices are stored in a single, unified repository. This approach allows developers to access everything from one place, streamlining collaboration across teams working on different but related parts of the project.
- Multi-repo: In a multi-repo structure, the codebase is split into several repositories, typically one per project, service, or module. This setup allows for better modularity and individual management of each repository, often with greater autonomy and responsibility distributed across different teams.
Mono-repo example
├── apps
│ ├── base
│ ├── production
│ └── staging
├── infrastructure
│ ├── base
│ ├── production
│ └── staging
└── clusters
├── production
└── stagingMulti-repo example
Platform admin repository example
├── teams
│ ├── team1
│ ├── team2
├── infrastructure
│ ├── base
│ ├── production
│ └── staging
└── clusters
├── production
└── stagingDevelopment Team repository example
└── apps
├── base
├── production
└── stagingComparison of Mono-repo and Multi-repo Approaches
| Criteria | Mono-repo | Multi-repo |
|---|---|---|
| 1. Codebase Structure | Single, unified repository for all projects and modules | Multiple repositories, each focused on one project/module |
| 2. Code Sharing | Easy to share code between modules | Code sharing requires more coordination between repositories |
| 3. Version Control Complexity | One repository with a simpler versioning scheme | Each repo has its own version control, potentially leading to inconsistency |
| 4. Dependency Management | Unified dependency management across all projects | Each repository manages its dependencies separately |
| 5. Build Complexity | Builds can be more complex and time-consuming as the entire repo is built | Builds are isolated per repository, typically faster |
| 6. CI/CD Integration | Centralized CI/CD pipelines; requires handling large builds | CI/CD pipelines are easier to manage for each smaller repo |
| 7. Cross-team Collaboration | Better collaboration as teams work on the same repository | Requires more coordination between teams across repositories |
| 8. Testing | Easier to run integration tests across all projects | Unit and integration tests are limited to individual repositories |
| 9. Code Review and PR Management | Centralized and consistent process for PRs and code reviews | Each repository has its own PR and code review process |
| 10. Scaling Challenges | Scalability can be an issue as the repository grows very large | Repositories remain smaller and easier to manage individually |
| 11. Conflict Resolution | More frequent merge conflicts as more people work in the same repo | Less frequent conflicts, isolated per repository |
| 12. Onboarding New Developers | Easier since all code is in one place; no need to switch repos | Requires familiarity with multiple repositories and workflows |
| 13. Tooling | Requires advanced tooling to manage the larger repository | Tooling is simpler as each repository is small and independent |
| 14. Security and Access Control | Harder to restrict access as everyone has access to the entire repo | Easier to manage permissions at a repository level |
| 15. Release Management | Releases are managed centrally for all projects | Each repository has independent release cycles |
Conclusion
Both mono-repo and multi-repo approaches have their pros and cons, and the decision on which one to adopt depends on several factors, including team size, project complexity, and organizational needs.
- Mono-repo is ideal for organizations seeking strong cross-team collaboration, streamlined code sharing, and unified dependency management. However, it can introduce scalability challenges and increased complexity for larger projects.
- Multi-repo, on the other hand, offers better autonomy, modularity, and scalability as each project can be managed independently. But it requires more coordination across teams and may result in code duplication and inconsistency.
Ultimately, there’s no one-size-fits-all solution, and many companies adopt a hybrid approach that combines the benefits of both models, depending on their use case.