Most Next.js projects start clean and degrade as features pile on. The difference between a codebase that stays maintainable and one that doesn't usually comes down to a handful of early decisions.
Route handlers and server components should call into a thin data-access layer rather than embedding queries directly. This makes it trivial to swap a data source, add caching, or write tests later.
Grouping components, hooks, and types by feature — rather than by file type — keeps related code close together and makes it obvious what can be deleted when a feature is retired.
Design your schema and relationships before writing UI. Retrofitting a data model after the UI is built almost always costs more than getting it right up front.
These aren't exotic techniques — they're the same discipline that separates production-grade software from a fast demo.