What Is The Onion Architecture?

Onion Architecture, or Hexagonal Architecture, is a software design pattern separating an application’s core logic from the surrounding infrastructure. It is designed to create a flexible and decoupled architecture that is easy to test and maintain.

The Onion Architecture is a software development approach commonly associated with Domain-Driven Design (DDD). This is due to its focus on modularity and separation of concerns, which are also crucial principles in DDD. Like DDD, the Onion Architecture emphasizes the importance of understanding the problem domain before designing and developing the software system. It aims to create a design that reflects the underlying domain model, thus ensuring that the software meets the business needs.

The Onion Architecture promotes the concept of a clean separation of concerns and the use of interfaces to ensure that the different components of the system can work together seamlessly. It helps to create a flexible and maintainable software system that is easy to understand and evolve.
However, the Onion Architecture is not a specific part of the DDD methodology, and it can be used independently of DDD as a general design pattern. It is primarily focused on the overall structure and organization of the codebase rather than on the specific domain concepts and relationships central to DDD. So it is not a kind of DDD, but it is often used in conjunction with DDD to create a well-structured and maintainable codebase that reflects the underlying domain model.