Hexagonal architecture

An architectural pattern that decouples core business logic from external systems using ports and adapters to ensure painless testing and swap-ready infrastructure.

Created by Alistair Cockburn in 2005, Hexagonal Architecture (also known as Ports and Adapters) isolates an application's core domain logic from outside influences like databases, user interfaces, and third-party APIs. By defining strict boundaries through ports (interfaces) and adapters (implementations), developers can write pure, technology-agnostic business rules that remain completely testable in isolation. This setup means you can swap a PostgreSQL database for MongoDB, or replace a REST API with a gRPC CLI, without touching a single line of your core application logic.

https://alistair.cockburn.us/hexagonal-architecture/