How would you structure a production ASP.NET Core application using C#?

A production ASP.NET Core application should have clear boundaries while remaining proportional to the application's complexity.

The presentation layer handles HTTP endpoints, model binding, authentication/authorization integration, and response formatting. Application services or use cases coordinate business workflows. Domain models contain important business rules where appropriate. Infrastructure handles EF Core, external APIs, file storage, email, caching, and other technical integrations.

Dependency injection connects abstractions to implementations. DTOs should define API or UI contracts rather than exposing persistence entities unnecessarily. Database operations should use efficient LINQ, appropriate projections, pagination, indexes, and asynchronous I/O. Read-only EF Core queries often benefit from AsNoTracking.

Cross-cutting concerns such as exception handling, validation, logging, security, caching, and observability should be implemented consistently. Automated tests should cover important business behavior and integration boundaries.

The architecture should be simple enough to understand but structured enough to allow the application to evolve without controllers, services, and database code becoming tightly coupled.