Distributed system patterns

Distributed systems can get complex quickly. Over the years, many patterns have emerged to help us manage and thrive in this complexity. We will explore some of them next.

CQRS

Those who know a little about CQRS might be surprised that one of the first mentions of it in a book about DDD is in the distributed system section. Let’s dig into what it is, and then we can revisit this point.

In traditional systems and the monolithic system we built in Chapter 5, Applying DDD to a Monolithic Application, we use the same data model and repository to create and read a database from our database. This can work well in a lot of use cases, but as systems develop complexity, it can be hard to manage all the queries and mapping between the data and service layer. Furthermore, systems often have different requirements for reading and writing. For example, a system for capturing analytics might write a lot more than it is read. It could make sense to treat...