Problem: Need complete audit trail of all changes to application state.
Solution: Use an append-only store to record the full series of events that describe actions taken on data in a domain.
When to Use:
- Requiring complete audit trail
- Implementing temporal queries (point-in-time state)
- Supporting event replay and debugging
- Implementing CQRS with eventual consistency
Implementation Considerations:
- Store events in append-only log
- Rebuild current state by replaying events
- Implement event versioning strategy
- Handle event schema evolution
- Consider storage growth over time
- Implement snapshots for performance