CQRS and Event Sourcing Patterns

Expert guidance for implementing Command Query Responsibility Segregation (CQRS) and Event Sourcing patterns to build scalable, auditable systems with complete historical tracking and optimized read/write models.

When to Use This Skill

• Building systems requiring complete audit trails and compliance
• Implementing temporal queries ("show me the state at time T")
• Designing high-scale applications with complex domain logic
• Creating systems with significantly different read and write patterns
• Building event-driven architectures with historical replay capability
• Implementing systems requiring multiple read model projections
• Designing applications where understanding "what happened" is critical
• Building collaborative systems with conflict resolution needs

Core Principles

1. Command Query Separation

Separate operations that change state (commands) from operations that read state (queries).