As our company developed through startup and scale up phases, our systems grew larger and more complex. Our usage increased dramatically and our requirements ballooned.

In this session, we will look at how our software and architecture developed into a Conway’s law spider web of interdependent services. We will examine how a start-up environment and the need to find product market fit quickly encourages developers to favour feature and product development over scalable, re-usable and DRY code.

We will show how we used domain driven principles to give our systems structure and provide guidance to our developers. We will study the complexities of refactoring using a domain driven approach in a large existing code base and share some approaches that worked for us.

First delivered at QCon 2025. This is a 45 minute presentation. The target audience is both new and experienced DDD practitioners or architects and developers seeking to apply DDD principles to their existing codebase.