CQRS comes with separating commands and query databases.

 So this required syncing both 2 databases with offering event-driven architectures.

 And with Event-driven architectures, there are some new patterns and practices that should be considered when applying CQRS.

The event Sourcing pattern is the first pattern we should consider using with CQRS. 

Mostly CQRS is using “Event Sourcing pattern” in Event-Driven Architecture. 

So after we have learned the CQRS we should learn the “Event Sourcing pattern”, because CQRS and “Event Sourcing pattern” is the best practice to use both of them.

https://medium.com/design-microservices-architecture-with-patterns/cqrs-design-pattern-in-microservices-architectures-5d41e359768c