How a Monorepo Keeps Multiple Projects in Sync - From Shared Code to Atomic Deployments

Copy-Paste Development Every company that runs more than one project eventually faces the same problem. It starts small. Project B needs the same user authentication logic as Project A, so someone copies the auth module over. A few months later, Project C launches and borrows the same code - plus some API utilities from Project B. By the time Project D kicks off, there are four slightly different implementations of the same auth flow, three versions of the same API types, and no one remembers which project has the "correct" version. Each project drifts. Different ESLint configs. Different TypeScript strictness levels. Different folder structures. A junior developer joins Project C and learns patterns that don't exist in Project A. A bug gets fixed in one project's copy of a utility but never propagated to the others. The usual answer to this is internal npm packages. Extract the shared code, publish it to a private registry, and have each project depend on it. This helps, but it introd