event-sourcing

You can implement an event store by creating an aggregate, appending a sequence of domain events, and replaying them to produce current state. This Skill provides the core mechanics for capturing state changes and building projections for querying the reconstructed data.

You can replay domain events by loading the append-only event sequence for an aggregate and applying each state change in order. This Skill provides the mechanics to replay the event store, rebuild aggregates, and generate queryable projections from the historical data.

Event sourcing is well-suited for compliance-heavy financial systems because it captures every state change as an immutable domain event. This guarantees a complete audit trail and enables temporal queries to reconstruct any past state for regulatory compliance and debugging.

You need snapshots in an event-sourced system when replaying long sequences of domain events for a single aggregate becomes a performance bottleneck. Snapshots save the aggregate state at intervals, reducing the number of events that must be processed during event replay.

A limitation of an append-only event store is that updating or deleting past domain events is disallowed, which complicates schema migrations and error corrections. Additionally, reconstructing current state requires event replay, potentially creating read latency without optimized projections or snapshots.