implement-event-sourcing

Implement event sourcing by defining immutable domain events, persisting them to an append-only event store with versioning, and rebuilding state through replay. This approach separates write models from read projections, fitting naturally with CQRS and DDD architectures.

Rebuild aggregate state by replaying the immutable event log sequentially to reconstruct current domain state. To optimize performance for large event streams, periodically save aggregate snapshots and restore from the nearest snapshot before replaying subsequent events.

Evolve event schemas in an event-sourced system by applying upcasters to transform outdated events into the current version. This allows you to handle schema changes without migrating the append-only event store, ensuring replayable history remains compatible.

Generate read models by building projections that subscribe to the event log and derive query-optimized views. This allows you to create tailored read models for specific queries while the event store remains the single source of truth for domain state.

Yes, event sourcing fits microservices and event-driven workflows by using an append-only event store to persist state changes. It enforces optimistic concurrency control and enables reliable event replay across distributed services.

Use snapshots in an event-sourced domain when replaying large event streams becomes a performance bottleneck during aggregate reconstruction. Snapshots capture the state at a specific version, reducing the number of events you must replay to restore current domain state.