3 years ago

For many developers, event sourcing is a magical beast that's used to build extremely complex, often distributed projects. And there's good reason for that: event sourcing is a pattern that forces code to be built in a way that fits those complex projects exceptionally well.

When I discuss event sourcing, people often assume that it comes with significant overhead, and that that overhead isn't justified in smaller projects.

Not just can we query these events, we can also use the event log to reconstruct past states, and as a foundation to automatically adjust the state to cope with retroactive changes.The fundamental idea of Event Sourcing is that of ensuring every change to the state of an application is captured in an event object, and that these event objects are themselves stored in the sequence they were applied for the same lifetime as the application state itself."

With event sourcing, the question of "is a cart checked out" should be answered by looking at the events that happened related to that cart, and not by looking at a cart's status.