Eseményforrás

Eseményforrás, often translated as "event sourcing," is an architectural pattern for designing applications. Instead of storing the current state of an application directly in a database, event sourcing stores a sequence of immutable events that have happened over time. Each event represents a change to the application's state. This sequence of events is often referred to as the "event log" or "event stream."

To determine the current state of the application, one would replay all the events from the beginning of the event log. This approach has several advantages. It provides a complete audit trail of all changes, making debugging and historical analysis easier. It also allows for rebuilding the application's state at any point in time, which can be useful for auditing or recovering from errors.

Event sourcing decouples the act of recording changes from the act of reading or querying data. This can lead to more flexible systems. For instance, different read models can be derived from the same event stream, optimized for various query needs. However, implementing event sourcing can be more complex than traditional state-based storage, and managing the event log's growth and performance requires careful consideration. It is particularly well-suited for domains where tracking history and state changes is critical.