Nlayered

Nlayered is a software architecture pattern that organizes an application into N distinct layers, where N is an arbitrary positive integer. It generalizes traditional multilayer or n-tier architectures by allowing any number of layers beyond the conventional three or four. Each layer has a defined responsibility and communicates with the layer directly beneath it through well-defined interfaces, maintaining separation of concerns and enabling modular development and testing.

Typical layers include a presentation layer for user interfaces, an application or service layer that coordinates use cases, a domain or business logic layer that enforces rules and invariants, a data access layer that abstracts persistence, and sometimes an integration adapters or an infrastructure layer that handles cross-cutting concerns such as logging, security, and messaging. The exact composition of layers depends on the project, technology stack, and performance goals.

Key characteristics of Nlayered include explicit boundaries, dependency direction from higher to lower layers, and the use of data transfer objects or domain models to prevent leakage of implementation details. The pattern supports testability and maintainability but can introduce additional indirection and potential performance overhead if layers are too fine-grained or if communication across layers is excessive.

When applying Nlayered, teams should define clear responsibilities for each layer, establish stable interfaces, apply dependency inversion principles, and minimize direct coupling between non-adjacent layers. Techniques such as DTO mapping, domain-driven design, and API gateways or adapters help maintain boundaries. Documentation and code governance help avoid layer leakage and keep the architecture coherent as the system evolves.

Nlayered is closely related to other architectural patterns such as layered architecture and n-tier architecture, and it is commonly used in enterprise and web applications. In modern contexts, variations of Nlayered can map across service boundaries in microservice architectures, where each service implements its own layers. Critics warn that over-engineering the layer count can add complexity for small or fast-moving projects.