Clean Architecture and the 'Don't Repeat Yourself' (DRY) Trap.

In CA, it is often better to duplicate data structures (Mappers/DTOs) than to couple layers together.

Developers often try to use the same 'User' class for the DB, the Domain, and the UI to be DRY. This is a mistake in CA. These models change for different reasons. Coupling them means a DB change can break your UI. CA prioritizes 'Decoupling' over 'DRY' at the boundaries.