Implementing Domain-Driven Design

Examining Areas of CQRS

Let’s step through each of the major areas of this pattern. We can start with the client and query support and move through to the command model and how updates to the query model are done.

Client and Query Processor

The client (at the far left in the diagram) may be a Web browser or a custom desktop user interface. It uses a set of query processors running on a server. The diagram doesn’t show architecturally significant divisions between tiers on the server(s). Whatever tiers exist, the query processor represents a simple component that only knows how to execute basic queries on a database, such as a SQL store.

There are no complex layers here. At most this component runs a query against the query store database and ...