Event Sourcing

Build auditable systems by storing complete history of state changes as immutable events rather than current values.

Context

You are designing a system requiring auditability, temporal analysis, or replay capability. Event sourcing provides complete history and enables powerful event-driven architectures. Read domain requirements and existing event-driven patterns.

Domain Context

Based on Greg Young's event sourcing work and CQRS patterns:

• Event Store: Append-only log of domain events; immutable, ordered
• Aggregate Reconstruction: Replay events to reconstruct current state on-demand
• Snapshots: Optimize replay by storing intermediate state; trade storage for speed
• Event Versioning: Events evolve; handle schema changes in replays
• Projections: Materialize different views from event stream (CQRS read models)

Instructions