Comparing complexity in MVC+CRUD vs. CQRS+ES

By Javier Toledo

This research explores the effectiveness of Domain-Driven Design (DDD) using Command Query Responsibility Segregation (CQRS) and Event-Sourcing (ES) patterns in simplifying and managing the complexity of large-scale software development projects. It takes a critical look at the common Model-View-Controller (MVC) pattern used in major frameworks like Spring Boot, NestJS or Ruby on Rails, which often leads to increased code complexity and difficult communication between product and engineering teams. The paper discusses the advantages of DDD, CQRS, and ES and their potential in reducing coupling, thus managing compound complexity effectively. It presents an in-depth comparison study between the MVC and the CQRS+ES approach, using quantitative metrics such as number of files created, functions/classes refactored, lines of code added or deleted, imported files and function calls. This study aims to illustrate the impact of these methodologies on the organization and interdependence of the codebase, and to offer valuable insights for improved software development practices.