lean-project-structure

Separate the codebase into layers: thin entry/routing files, dedicated business logic modules, isolated data access, and logic-free presentation. Give each file one responsibility, cap function size around 40 lines, and document the layout for future contributors.

Refactor incrementally rather than rewriting everything at once. Extract business logic out of route handlers into named service modules, move data access into its own layer, and keep the entry file thin. Split functions that exceed the size limit.

Follow the framework's expected layout rather than fighting it. Apply the same layering principles within the framework's conventions, keeping routes thin and business logic in dedicated modules.

A single file is fine for tiny scripts, prototypes, and throwaway code. Over-structuring small utilities adds overhead without benefit; apply layered structure only when the project is expected to grow or be maintained.

Apply the same layer boundaries per package within the monorepo. Keep shared code in a clearly named shared module rather than duplicating it, and maintain single-responsibility files inside each package.