This talk will present a case study of utilizing Domain-Driven Design (DDD) methodologies to address the challenges of evolving Wikipedia's underlying system architecture. Wikipedia is a 23-year-old open-source monolith that serves billions of reads and millions of simultaneous writes, with a unique combination of dynamic user-generated content and workflows. The scale, complexity, and socio-technical nature of Wikipedia make it a challenging environment for applying DDD. This talk will discuss the process of mapping the system to understand potential pitfalls, discover opportunities, and inform product strategy.