What is Clean Architecture in iOS and how do you implement it at scale?

Clean Architecture separates code into layers: Presentation, Domain, and Data.

At scale, Clean Architecture enforces strict dependency rules where outer layers depend on inner layers only. The Domain layer contains business rules and is independent of frameworks. The Data layer handles API, database, and caching. The Presentation layer manages UI and state. This structure allows independent testing, easier refactoring, and long-term maintainability.