So we can say that CQRS separates reads and writes into different databases, Commands performs update data, Queries performs read data.

Commands should be actions with task-based operations like “add item into shopping cart” or “checkout order”. So commands can be handle with message broker systems that provide to process commands in async way.

Queries is never modify the database. Queries always return the JSON data with DTO objects. By this way, we can isolate the Commands and Queries.

In order isolate Commands and Queries, its best practices to separate read and write database with 2 database physically. By this way, if our application is read-intensive that means reading more than writing, we can define custom data schema to optimized for queries.

Materialized view pattern is good example to implement reading databases. Because by this way we can avoid complex joins and mappings with pre defined fine-grained data for query operations.

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