Where is the business logic implemented in an application using Clean Architecture principles?

In Clean Architecture, business logic is implemented in the Use Cases (or Interactors) layer. This layer contains the application's rules and defines how data is processed and what actions are performed, independently of the UI, database, or external services. Use Cases take input data, apply business rules, and return results, ensuring independence from implementation details.

For example, if you have an order application, the logic for calculating order cost and checking product availability would reside in the Use Cases.