Whether to keep multiple projects in one shared repository (monorepo) or split them into independent repositories (polyrepo) is a genuine architectural decision with real trade-offs, not just a style preference.
Monorepo Advantages
- Atomic cross-project changes — updating a shared library and all its consumers in a single commit/PR
- Simplified dependency management — no version mismatches between internal packages
- Unified tooling, CI, and code review standards across the whole codebase
Polyrepo Advantages
- Clear ownership boundaries — a team’s repo is genuinely theirs, no risk of accidental cross-team changes
- Independent versioning and release cadence per project
- Smaller checkouts and simpler CI configuration per repo
The Real Cost of Monorepos at Scale
# At genuine scale, plain git commands become painfully slow on a monorepo # without specialized tooling - this is why companies like Google, Meta, and # Microsoft built custom tooling (Bazel, Buck) specifically to make # monorepos tractable at their size
A monorepo without investment in proper build tooling (incremental builds, selective test running based on what actually changed) becomes genuinely painful as it grows — the “just use a monorepo” advice from big tech companies often glosses over the substantial tooling investment that makes it work at their scale.