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

• Identify aggregate boundaries and event streams
• Design events as immutable facts
• Implement command handlers and event application
• Build projections for query requirements
• Design saga/process managers for cross-aggregate workflows
• Implement snapshotting for long-lived aggregates
• 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-*