Evolve the domain
Over time, we learn more and more about the requirements of our software, and we can make better and better decisions about the best architecture style. The application might evolve from a collection of simple CRUD use cases to a rich domain-centric application with a lot of business rules. At this point, the Hexagonal Architecture style becomes a good option.
It should have become clear in the previous chapters that the main feature of a Hexagonal Architecture style is that we can develop domain code free from diversions, such as persistence concerns and dependencies on external systems. In my opinion, evolving domain code free from external influence is the single most important argument for the Hexagonal Architecture style.
This is why this architecture style is such a good match for DDD practices. To state the obvious, in DDD, the domain drives the development, and we can best reason about the domain if we don’t have to think about persistence concerns...
