Aggregates are one of the more challenging aspects of tactical modeling. Developers often end up with large clusters of objects that do not give good performance and scalability. In this three-part series, Vaughn Vernon walks through some common design pitfalls, discusses the pros and cons of various aggregate modeling choices, and provides rules of thumb to guide modeling of aggregates. He de-emphasizes such concerns as navigation through object graphs and instead focuses on digging out real consistency constraints in the business domain, with tips to help the team sift through the usual pile of competing use-cases.

Vaughn’s concrete rules spell out the current consensus view of DDD leaders on the style of aggregates that help place development on a more solid footing.