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Day 41Sprint 5 • Clean Architecture & Cloud
2 Hours
Day 41: Clean Architecture, Domain Driven Design & CQRS with MediatR
Clean Architecture (popularized by Robert C. Martin "Uncle Bob") organizes software into concentric circles of responsibility. The core business rules (Domain & Application) remain completely independent of UI frameworks, database engines, and third-party cloud SDKs.
Master the 4 layers of Clean Architecture (Domain, Application, Infrastructure, Presentation)
Implement CQRS (Command Query Responsibility Segregation) pattern
Decouple business use-cases using MediatR (IRequest<T> and IRequestHandler<TReq, TRes>)
Enforce the Dependency Inversion Principle where outer layers depend on inner core
Core Architectural Insights
- Domain Layer has zero external dependencies; pure enterprise business logic and entities
- Application Layer defines use cases, DTOs, and CQRS commands/queries via MediatR
- Infrastructure Layer implements database access (EF Core), cloud services, and email providers
- Presentation Layer (Web API, Blazor) acts purely as an entry-point adapter
Real-World Developer Analogy
Think of Clean Architecture like a high-end luxury watch. The golden gears (Domain logic) are protected inside a sealed case. The watch strap (UI) or the battery (Database) can be swapped in 2 minutes without ever touching or damaging the precious internal movement.