A Comparative Case Study on Migrating a Modular Monolith Java App to IaaS and PaaS on Azure and AWS

The paper presents a comparative study of cloud migration for modular monolith Java Spring application, focusing on IaaS and PaaS deployment models across AWS and Azure. The study examines the technical and operational challenges of adopting each model, highlighting the trade-off between infrastructure control and management abstraction. Through a practical migration case study, we analyze the deployment process using AWS EC2 and Azure Virtual Machines for IaaS, as well as AWS Elastic Beanstalk and Azure App Services for PaaS. The findings illustrate that IaaS offers high configurability and allows for the precise replication of on-premise environments, but it demands significant technical expertise. In contrast, PaaS enables streamlined deployment and scalability but may limit customization and can introduce additional financial implications. The analysis further contrasts the two cloud platforms regarding ecosystem integration, deployment tools, hybrid cloud support, and service maturity. Key challenges encountered during migration, such as upgrading various frameworks, configuring secure connectivity, deploying workflows, and establishing CI/CD pipelines, are thoroughly documented. A comparative analysis provides insights into the financial impact of each model. This work serves as a practical guide for decision-makers involved in enhancing legacy applications. It offers criteria for selecting the appropriate cloud model and provider based on strategic, technical, and economic considerations.