The Modular Monolith Boundary I Couldn't Take Back

This article discusses the challenges of maintaining a modular monolith architecture in software engineering. The author describes a system where two modules—Catalog and Collaboration—were initially separated by domain boundaries and asynchronous event communication. However, over time, feature requirements (like live pricing and immediate catalog updates) slowly wove the modules back together, making the boundary effectively irreversible. The article explores the trade-offs between decoupling and business needs, highlighting how eventual consistency can conflict with real-time correctness demands. It serves as a cautionary tale for developers and architects about the hidden costs of modular design decisions.