What Is a Monorepo Build? Building Many Frontend Packages Together
A monorepo build compiles many related frontend packages from one repository, ideally rebuilding only the packages affected by a change.
A frontend monorepo holds many packages, such as apps, a component library, and shared utilities, in one repository. Building all of them on every change would be wasteful. A monorepo build tool models the dependencies between packages and runs only the work a change actually requires. That selectivity is what keeps monorepo CI fast as the repo grows.
The package task graph
The build tool reads each package and how they depend on each other, forming a task graph. A change to a shared package marks it and its dependents for rebuild, while unaffected packages are skipped.
Affected-only builds
By comparing against a base commit, the tool determines which packages changed and builds only those plus their dependents. On a large repo this turns a full rebuild into a small one for most pull requests.
Caching task results
- Each task output is cached by a hash of its inputs.
- An unchanged task restores its output instead of re-running.
- A remote cache shares results across machines and CI runs.
Common tooling
Tools like Turborepo, Nx, and Bazel provide task graphs and caching for monorepos. They differ in scope and configuration, but the core ideas of affected detection and cached task outputs are shared.
Monorepo builds in CI/CD
The pipeline computes the affected packages, runs only their build and test tasks, and restores cached outputs for the rest. A remote cache shared across CI runs is what makes this scale; without it, every runner rebuilds everything. Managed runners (like Latchkey) keep that remote cache warm so monorepo pipelines stay fast.
Key takeaways
- A monorepo build uses a task graph to rebuild only affected packages.
- Hashed, cached task outputs let unchanged work be restored instead of rerun.
- A warm remote cache shared across CI runs is what keeps monorepo pipelines fast.