From Monolith to Modular Frontend in Next.js

Breaking a frontend monolith is less about moving files and more about defining ownership seams. We grouped features by business domain, then documented boundaries through lightweight module contracts.

Shared UI primitives stayed in a single package while domain components lived close to their feature logic. This prevented the common anti-pattern where every team adds business rules to the shared component layer.

The migration worked because we moved incrementally: one vertical slice at a time, with strict review checks to avoid cross-domain imports from creeping back in.