CQRS and the Mediator Pattern

Command Query Responsibility Segregation (CQRS) is an architectural pattern that separates read and write operations into distinct models, enabling independent scaling and optimization of each responsibility. The Mediator pattern, implemented in .NET via the MediatR library, provides a centralized request handler that decouples command/query senders from their implementations. Together, these patterns create applications that are testable, maintainable, and aligned with SOLID principles—critical for modern enterprise .NET development.

This series takes you from zero-to-production understanding of CQRS and MediatR. You'll learn the fundamental differences between CQRS and traditional MVC, implement command and query handlers with MediatR, build robust validation and logging pipelines, architect read/write separation for real-world performance, handle errors gracefully, and finally assemble a complete CQRS application end-to-end. Each tutorial is independently complete yet builds on prior patterns, so you can apply these concepts immediately in your next .NET project.

Articles in this series

• What is CQRS? Understanding Command Query Responsibility Segregation
• CQRS vs MVC: Key Differences and When to Use Each Pattern
• Introduction to MediatR: Building the Mediator Pattern in .NET
• Creating Commands and Handlers in MediatR: Step-by-Step
• Building Query Handlers with MediatR for Read Operations
• Validation Pipeline Behaviors in MediatR: Tutorial
• Implementing Logging with MediatR Behaviors: Step-by-Step
• CQRS Read/Write Separation: Advanced Data Architecture
• Error Handling and Exceptions in MediatR: Best Practices
• Building a Complete CQRS App with MediatR: Full Tutorial