SOLID & Design Patterns Interview Question #111

What is the Service Layer Pattern?

Architectural Patterns, Application Boundaries & Distributed Design Patterns Senior Advanced

Quick Interview Answer

The Service Layer Pattern defines an application boundary containing operations available to clients. It coordinates use cases and separates controllers or UI code from domain and persistence details.

Detailed Explanation

A service layer should not become a dumping ground for all logic. Business invariants should remain in appropriate domain objects, while orchestration belongs in application services.

Code Example

public interface IOrderApplicationService
{
    Task<Guid> PlaceOrderAsync(
        PlaceOrderRequest request);
}

public class OrdersController
{
    private readonly IOrderApplicationService _orders;
}