Monorepo vs polyrepo: choosing the right repository structure

The monorepo versus polyrepo debate is one of the most persistent disagreements in software engineering. Both approaches have passionate advocates and real tradeoffs. The right choice depends on your team size, tooling maturity, and project complexity.

Monorepos store all code for a project in a single repository. This provides unified versioning, atomic cross-project changes, shared tooling configuration, and simplified dependency management. A monorepo makes it easy to refactor across project boundaries and find code.

Polyrepos use separate repositories for each project or service. This enables independent versioning, access control, and CI/CD for each repository. Teams can move at their own pace without being blocked by other teams' changes. Polyrepos are simpler to set up and maintain.

The most common pain point with monorepos is build and test times. As the repository grows, building and testing everything on every change becomes slow. This requires sophisticated build tooling that can determine what needs to be rebuilt and what can be cached.

Polyrepos suffer from dependency management challenges. Shared libraries must be published and versioned. Cross-repository changes require coordinated releases. API changes in one repository break dependent repositories until they update their dependencies.

Tooling support matters. Monorepo tooling like Nx, Turborepo, and Bazel provides build caching, dependency graph analysis, and targeted testing. These tools make monorepos practical at scale. Without them, monorepos become unwieldy as they grow.

Start with a monorepo for most projects. The simplicity of having everything in one place outweighs the scaling concerns for most teams. Move to polyrepos only when you have clear evidence that the monorepo is slowing your team down typically when you have multiple independent teams working on independently deployable services.

Consider a hybrid approach. Use a monorepo for related projects within a team and separate repositories for unrelated initiatives. The goal is to minimize coordination overhead without forcing unrelated projects to share infrastructure.

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Rizwan Saleem | https://rizwansaleem.co