Fundamentals of Software Architecture, 2nd Edition

Chapter 11. The Modular Monolith Architecture Style

Thanks to the widespread adoption of domain-driven design (DDD), as well as increased focus on domain partitioning, the modular monolith architectural style has gained so much popularity since we wrote the first edition of this book in 2020 that we decided to add a chapter to the second edition describing (and rating) it.

Topology

As the name suggests, the modular monolith architecture style is a monolithic architecture. As such, it’s deployed as a single unit of software: a web archive (WAR) file, a single assembly in .NET, an enterprise archive (EAR) file in the Java platform, and so on. Because modular monolith is considered a domain-partitioned architecture (one organized by business domains rather than technical capabilities), its isomorphic shape is defined as a single deployment unit with functionality grouped by domain area. Figure 11-1 illustrates the typical topology for modular monolith.

To get a sense of the nature of modular monolith’s domain focus, consider the traditional layered architecture (described in Chapter 10). Its components are defined and organized by their technical capabilities: Presentation, Business, and Persistence layers, and so on. For example, the presentation logic for maintaining customer profile information might be represented by a component with the namespace com.app.presentation.customer.profile. The third node in the namespace represents the layer’s technical concern (in this case, the ...