event-sourcing

To design a backend architecture with event sourcing and CQRS, model domain events first, separate commands from events, use an append-only event store, and implement projections to build read models from the immutable event history.

Use event sourcing for domain-driven systems that require a full history of changes, such as orders, bookings, or inventory. It is ideal when you need auditing, history replay, or complex state reconstruction from immutable domain events.

Separate commands from events by treating commands as intent-driven requests that change state, and events as immutable facts that have already occurred. Commands are validated by aggregates, which then append resulting domain events to the event store.

Handle read models in event sourcing by building projections that subscribe to the append-only event store. These projections process domain events sequentially to create query-optimized views, reducing the need to replay the entire event history for every read request.

Yes, event sourcing and CQRS are well-suited for inventory and booking systems. They handle state changes by appending immutable domain events, allowing accurate history tracking, reliable auditing, and robust state reconstruction for complex domain logic.

An append-only event store requires careful schema evolution and projection management to avoid performance bottlenecks during history replay. Without snapshots, reconstructing large aggregates from a long event history can degrade read and write performance.