Domain Driven Design

In a recent video I did about Domain-Driven Design Misconceptions, there was a comment that turned into a great thread that I want to highlight. Specifically, somebody left a comment about their problem with Aggregates in DDD. Their example: if you have a chat, it has millions of messages. If you have a user, it has millions of friends, etc. It’s impossible to make an aggregate big enough to load into memory and enforce invariants. So the example I’m going to use in this post is the rule: a group chat cannot have more than 100,000 members. The assumption here… Read More »Aggregates in DDD: Model Rules, Not Relationships

Domain-Driven Design misconceptions often come from treating DDD like a checklist of patterns. Have you ever looked into Domain-Driven Design and thought, “Wow, this is totally overkill”? Well, you’re not alone. And I kind of agree, but not for the reasons you might think. I say you’re not alone because of this meme I did a video about that keeps giving. Somebody replied, “Learning .NET DDD sent me back to learning MVC. It’s so stressful.” I was kind of confused by this, and then somebody else was as well, saying, “What is the connection from DDD to MVC? It’s design… Read More »Domain-Driven Design Misconceptions

What’s Double Dispatch? Well, before we get to what it is, there is a common belief in domain-driven design that you want to keep your domain pure, meaning no dependencies, no services, no distractions. I get it because you do not want that core logic coupled to infrastructure concerns like database calls. You want it to be deterministic because you want it to be testable. But somewhere along the way this advice turned into dogma that you cannot inject behavior into your domain. I am going to challenge that. If you are modeling your domain and capturing behavior, you can… Read More »Double Dispatch in DDD