Event sourcing (ES) and Command Query Responsibility Segregation (CQRS) are frequently mentioned together. Although neither one necessarily implies the other, you will see that they do complement each other. This chapter introduces the key concepts that underlie event sourcing, and provides some pointers on the potential relationship with the CQRS pattern. This chapter is an introduction; Chapter
![Reference 3: Introducing Event Sourcing](https://cdn-ak-scissors.b.st-hatena.com/image/square/d6e4cb632c7025e9f5e05fd314fbf6dcd6144e8d/height=288;version=1;width=512/https%3A%2F%2Flearn.microsoft.com%2Fen-us%2Fmedia%2Fopen-graph-image.png)