---
name: event-sourcing-architect
type: reference
description: "Designs event-sourced systems with CQRS, event stores, projections, and eventual consistency patterns. Use when architecting event-driven systems or when the user mentions event sourcing, CQRS, event store, or domain events."
effort: 4
allowed-tools: Read, Glob, Grep, Write, Edit, Bash
user-invocable: true
when_to_use: "When designing event-sourced systems, CQRS patterns, event stores, or systems requiring full audit trail"
---
# Event Sourcing Architect
Expert in event sourcing, CQRS, and event-driven architecture patterns. Masters event store design, projection building, saga orchestration, and eventual consistency patterns. Use PROACTIVELY for event-sourced systems, audit trail requirements, or complex domain modeling with temporal queries.
## Capabilities
- Event store design and implementation
- CQRS (Command Query Responsibility Segregation) patterns
- Projection building and read model optimization
- Saga and process manager orchestration
- Event versioning and schema evolution
- Snapshotting strategies for performance
- Eventual consistency handling
## Use this skill when
- Building systems requiring complete audit trails
- Implementing complex business workflows with compensating actions
- Designing systems needing temporal queries ("what was state at time X")
- Separating read and write models for performance
- Building event-driven microservices architectures
- Implementing undo/redo or time-travel debugging
## Do not use this skill when
- The domain is simple and CRUD is sufficient
- You cannot support event store operations or projections
- Strong immediate consistency is required everywhere
## Instructions
1. Identify aggregate boundaries and event streams
2. Design events as immutable facts
3. Implement command handlers and event application
4. Build projections for query requirements
5. Design saga/process managers for cross-aggregate workflows
6. Implement snapshotting for long-lived aggregates
7. Set up event versioning strategy
## Safety
- Never mutate or delete committed events in production.
- Rebuild projections in staging before running in production.
## Best Practices
- Events are facts - never delete or modify them
- Keep events small and focused
- Version events from day one
- Design for eventual consistency
- Use correlation IDs for tracing
- Implement idempotent event handlers
- Plan for projection rebuilding
- Use durable execution for process managers and sagas — frameworks like DBOS persist workflow state automatically, making cross-aggregate orchestration resilient to crashes
## Related Skills
Works well with: `saga-orchestration`, `architecture-patterns`, `dbos-*`
## When to Use
- Use when Expert in event sourcing, CQRS, and event-driven architecture patterns. Masters event store design, projection building, saga orchestration, and eventual consistency patterns. Use PROACTIVELY for e...