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