CQRS and Event Sourcing patterns for scalable, auditable systems with separated read/write models. Use when building audit-required systems, implementing temporal queries, or designing high-scale applications with complex domain logic.
Provides expert guidance for implementing CQRS and Event Sourcing patterns to build scalable, auditable systems with complete historical tracking. Use when designing applications requiring audit trails, temporal queries, or handling complex domain logic with different read/write scaling needs.
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references/best-practices.mdreferences/consistency-patterns.mdreferences/cqrs-patterns.mdreferences/event-sourcing.mdreferences/event-store-tech.mdExpert 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.
Separate operations that change state (commands) from operations that read state (queries).
| Commands (Write) | Queries (Read) |
|---|---|
| Express intent (CreateOrder, UpdatePrice) | Return data, never change state |
| Can be rejected (validation failures) | Can be cached and optimized |
| Return success/failure, not data | Multiple models for different needs |
| Change system state | Eventually consistent with writes |
Store state changes as immutable events rather than current state snapshots.
Traditional: Store what IS → UPDATE users SET email = 'new@email.com'
Event Sourcing: Store what HAPPENED → APPEND UserEmailChanged event
Result: Complete history, temporal queries, audit trail
Accept temporary inconsistency between write and read models for scalability.
| Task | Load reference |
|---|---|
| CQRS implementation patterns | skills/cqrs-event-sourcing/references/cqrs-patterns.md |
| Event sourcing & snapshots | skills/cqrs-event-sourcing/references/event-sourcing.md |
| EventStoreDB & Axon Framework | skills/cqrs-event-sourcing/references/event-store-tech.md |
| Consistency patterns | skills/cqrs-event-sourcing/references/consistency-patterns.md |
| Best practices checklist | skills/cqrs-event-sourcing/references/best-practices.md |
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