Software Architect's Handbook

Event-sourcing

A system can use a data store to read and update the application's current state, but what if there are requirements to know the details of the state changes that got us to the current point? With event-sourcing, the events that take place in a system, such as state changes, are persisted in an event store. Having a complete record of all the events that took place allows it to serve as a source of truth. Replaying events from an event log can be used to recreate an application's state.

Event-sourcing works in a similar way to a transaction log in a database system. The transaction log records all of the modifications that have been made to a database. This allows for rollbacks of transactions and also allows us to recreate ...