Migrating a Legacy System to a Microservice Architecture

Background: In software engineering, each software product has a life cycle that at some point results in a decision being made with regard to extending its maintenance or upgrading the system to a new platform and architecture via a re-engineering or migration process. However, sometimes this decision is a non-starter; the technical dept accumulates, and platforms cease to exist, meaning that there will always be a time when extending the life support of a legacy system is no longer simply an option, and the service must be modernized. Aim: In this paper, we focus on the migration processes, where a legacy system is updated to a microservice architecture, to understand the current state-of-the-art, applied industry practices and potential pitfalls or research gaps in the topic domain. The study aims to explore previous research to find related trends and expose gaps in the literature. Method: We conducted a systematic mapping study on the research trends within the topic of redesign and re-engineering projects related to microservice architectures to understand what we know about microservices, what the current research trends in the area are, and if possible, what the common nominators for successful migration processes are. Results: Our observations reveal that most microservice migration research is confined to journal articles and conference proceedings. However, a severe fragmentation in publication venues exists within the field. Furthermore, the focus of the research field is primarily on the transformation phase of the re-engineering process, with the majority of the contributions being managerial in nature, particularly of the process type. Additionally, over 50 % of the research conducted is empirical in nature. Conclusion: Based on the results, microservice migration research is maturing well; most of the research is empirical. The research field is scattered. There are notable technical, managerial, and organizational challenges and differing motivations. To better understand the motivations and challenges of the practitioners, we are going to conduct survey and interview studies within this field.