What is the difference between the Clean and the N-Tier Architectures?

The Clean and N-Tier architectures are two distinct approaches to software design, each with its own set of principles and objectives aimed at addressing different concerns in the development process.

N-Tier Architecture

N-Tier architecture, also known as multi-tier architecture, is a client-server architecture that divides the application into logical and physical layers. This architecture is characterized by its layering and separation of concerns, aiming to improve scalability and maintainability. The primary layers in N-Tier architecture include the presentation layer (UI), the business logic layer, and the data access layer. Each layer communicates with the layers directly above and below it, creating a stacked architecture where each layer depends on the layer below it. This architecture is tightly coupled to external frameworks and drivers, such as HTTP servers, ORMs, or SQL drivers, which it uses for communication with the database through layers of business logic and representation[1].

Clean Architecture

Clean Architecture, on the other hand, emphasizes modularity, flexibility, and testability. It is designed around the concept of separating the core business logic of an application from external concerns such as UI, databases, and other infrastructure. This separation is achieved through the use of Dependency Injection and clear interfaces, allowing for a loosely coupled design. In Clean Architecture, the application is structured into layers of adapters and externals (3rd party frameworks/drivers) around the core use cases of the application. The representation and the database layers are considered externals, which the application interacts with through adapters. This architecture makes it easier to test, develop, and maintain the application code, as it allows developers to focus on the application itself without concerning themselves with integration tests or mocking out ORMs to test the business logic. It also facilitates the replacement of external frameworks or drivers by simply writing new adapters[1].

Key Differences

• Layering and Separation of Concerns: N-Tier architecture focuses on a hierarchical model where each layer depends on the layer below it, emphasizing layering and separation of concerns for sca...