Using CQRS and Event Sourcing in the Architecture of Complex Software Solutions

Mantu Singh

Abstract: The article explores the theoretical and practical aspects of migrating complex software solutions built on traditional Domain - Driven Design to an architecture based on Command Query Responsibility Segregation (CQRS) combined with Event Sourcing. The analysis focuses on the key advantages and existing limitations of these approaches, including their impact on code complexity metrics, system performance, and infrastructure requirements (Event Store, message brokers). As an example, the article references the results of an experiment conducted by other researchers, comparing an initial task - tracking system with its CQRS and Event Sourcing - based version, demonstrating improved scalability alongside increased infrastructure complexity. The study provides recommendations on migration strategies (evolutionary or "cold"), methods for ensuring idempotency, and best practices for configuring monitoring and testing tools. The findings presented in the article will be of interest to researchers, software architects, and practitioners involved in the development of distributed systems seeking to implement CQRS and Event Sourcing paradigms to enhance scalability, fault tolerance, and consistency in complex software solutions within dynamic business environments.

Keywords: CQRS, Event Sourcing, Domain - Driven Design, cyclomatic complexity, architecture migration, high - load systems, idempotency, monitoring