CQRS/CQS is a way to share data over two micro services via common data source

 Best practice in micro service design is share nothing. every micro service have it own data store. This makes the micro services resilient against slow data provider and resilient against outages of data delivering micro services. But there is one way to speed up this micro service architecture. If you use the CQRS pattern (Query Responsibility Segregation) or CQS pattern (Query Command Separation), my favorite pattern, and combine it with micro services.

Service A write or modify data only e.g. import billing data as large CSV  from the main frame. And Service B (E-Commerce-Backend) read only the data. Service B doesn't alter the data, it's a read only service. Both services using the same data source. Under this conditions (CQS) a common data source is a save and easy way to handle common data in a micro service environment.