CI/CD Patterns for Monorepos#

A monorepo puts multiple packages, services, and applications in a single repository. This simplifies cross-package changes and dependency management, but it breaks the assumption that most CI systems are built on: one repo means one build. Without careful pipeline design, every commit triggers a full rebuild of everything, and CI becomes the bottleneck.

The Core Problem#

In a monorepo, a commit that touches packages/auth-service/src/handler.ts should build and test auth-service and its dependents, but not billing-service or frontend. Getting this right is the central challenge of monorepo CI.