deriving the current state from an event log also simplifies some aspects of concurrency control. Much of the need for multi-object transactions (see “Single-Object and Multi-Object Operations”) stems from a single user action requiring data to be changed in several different places. With event sourcing, you can design an event such that it is a self-contained description of a user action. The user action then requires only a single write in one place — namely appending the events to the log — which is easy to make atomic.
