Modernizing Legacy Systems with Microservices: A Roadmap

Legacy systems are long-lived applications, with obsolete technology and degraded architecture. These systems hamper digital transformation and innovation, and require a great amount of resources for maintenance. The modernization of monolithic legacy systems is a strategy to promote better evolution and maintenance, taking advantage of new technologies such as microservices. Microservice architectural style is a paradigm to develop systems as a suite of small and autonomous services, communicating through a lightweight protocol. However, the migration of legacy systems to microservices is complex. Although we can find several studies on this topic, they usually focus on specific activities, e.g., the identification of the microservice boundaries in the legacy code. Also, existing pieces of work do not cover real-world scenarios, since they do not take into account organizational, operational, and technical aspects. To overcome this limitation, in this paper we present a roadmap for modernizing monolithic legacy systems with microservices. The roadmap is distilled from the existing body of knowledge, describing common activities and input/output information. The proposed roadmap is composed of eight activities, grouped in four phases, namely initiation, planning, execution, and monitoring. The main contributions are: (i) serve as a basis for practitioners to plan, execute, and monitor the modernization process; (ii) be a reference for researchers to design new studies; and (iii) motivate tool builders to deal with existing needs.