# A Systematic Mapping Study on the Modernization of Legacy Systems to Microservice Architecture
## 2 Background and Related Work  
This section provides an overview of the background and related work that contributed to the development of our study. Initially, we report on the concepts of microservices and software modernization. We then address related work on the modernization of legacy systems based on microservices. According to [PERSON] and [PERSON] [10], the term \"Microservice Architecture\", or MSA, has been used to refer to a particular way of designing software applications as suites of independently deployable services. In short, the aforementioned authors presented a definition that researchers and practitioners have used in the literature to describe this architectural style as \"_an approach to developing a single application as a suite of small services_,each running in its own process and communicating with lightweight mechanisms, often an HTTP resource API (Application Programming Interface). These services are built around business capabilities and independently deployable by fully automated deployment machinery. There is a bare minimum of centralized management of these services, which may be written in different programming languages and use different data storage technologies._  
Drawing a parallel with other existing definitions in the literature on microservices, [PERSON] [11] mentioned that the term \"microservices\" refers to a software architecture concept associated with the decomposition of an application into smaller, independent functions that run in the infrastructure resources. [PERSON] [12] reinforces this idea by describing that microservices should be small and focused on performing a task efficiently and autonomously. As defined by IBM [13], microservices represent an architectural style in which large and complex applications are composed of one or more microservices. Finally, as outlined by [PERSON] and [PERSON] [14], microservices encompass a multitude of concepts that have emerged from software engineering best practices and the agile developer community and are strongly associated with the DevOps approach (Development and Operations). Based on the concepts reported in this section, it can be said that microservice architectures facilitate scalability and boost the development of solutions, thereby fostering innovation and reducing the time required to introduce new features into the market. Modernization can be defined as a transformation process in which the software system is adapted or refactored to meet new user requirements and adapt to new market technologies. In this direction, MSA offers several advantages, including a maintenance facility, faster time to market, and high scalability. These benefits are particularly sought after in systems that are considered legacy or monolithic, as evidenced by [PERSON] [12]. Despite the existence of various approaches related to modernization, the feasibility of developing a microservice-based application from scratch remains uncertain, particularly due to the constraints of cost and time. While there are initiatives in the literature, the decomposition of a system into microservices remains a challenging task due to the lack of a comprehensive guide that covers the entire process. This is because of the necessity of several iterations to identify suitable microservice limits [15]. [PERSON] et al. [7] conducted a tertiary study on the modernization of legacy systems with the implementation of MSA. Of the 20 secondary studies selected for analysis in this tertiary study, none of them addressed the research interest reported in this article. Based on the key findings of the above tertiary study, it can be said that this research topic is still emerging and is of common interest in both academic and industry segments. Moreover, by synthesizing insights from various secondary studies, the aforementioned study provides a comprehensive overview of motivations, the main architectural patterns organized in a taxonomy, the faced challenges, the expected benefits, and the macro-steps to conduct modernization.