juniorClean Architecture
What is the Interface Adapter layer?
Updated Apr 28, 2026
Short answer
This layer converts data from the format most convenient for use cases and entities to the format most convenient for external agencies (DB, Web).
Deep explanation
This layer contains Controllers, Presenters, and Gateways. It acts as a translator. For example, a Controller takes an HTTP request, extracts the relevant data into a DTO, and passes it to a Use Case. A Gateway (Repository implementation) takes a Domain Entity and converts it into a Database Row.
Real-world example
An Express.js Router or a SQL Repository implementation class.
Common mistakes
- Leaking HTTP status codes into the Use Case layer.
Follow-up questions
- Where does the data transformation logic reside?