# A Systematic Mapping Study on the Modernization of Legacy Systems to Microservice Architecture
###### Abstract
In summary, the investigation yielded evidence on a number of pertinent issues, including (i) the motivation behind organizations' decision to modernize their systems with the implementation of MSA, (ii) the challenges encountered during the modernization process, (iii) the anticipated benefits of modernization, (iv) the patterns adopted for modernization, and (v) the identification of the main step in the modernization process. Regarding the last item, the investigation has revealed that there is still much to be understood about the transition process from legacy systems to MSA. Therefore, further investigation is required to gain a deeper understanding of this topic. A comparison between the challenges and the modernization process reveals a dearth of methodological understanding and the requisite infrastructure to support the activities inherent in such a process [7]. In order to address this issue, we present in this article a comprehensive overview of the modernization of legacy systems based on MSA, focusing on the process activities. This overview is based on a mixed-method investigation composed of a systematic mapping study (SMS) and an empirical evaluation by industry practitioners. In short, the SMS is a technique that enables researchers to conduct a complete and fair evaluation of a research topic by using a trustworthy, rigorous, and auditable methodology with a well-defined strategy [8]. In order to establish a comprehensive and state-of-the-art overview, a total of 43 studies were selected for examination in this SMS. The objective of our investigation is to provide insights into the application domains, evaluation strategies, maturity level, quality attributes, and key activities identified in the design of the initiatives concerning the modernization of legacy systems based on MSA. As a result, a modernization process comprising six macro-activities was formulated, along with a set of steps for each activity. In the subsequent stage of our study, we submitted the SMS-derived modernization process to software industry practitioners from two companies for evaluation of the activities and steps associated with each activity. Next, we present a synthesis of the findings from our investigation for the benefit of stakeholders (i.e., researchers and practitioners):  
* A detailed and solid panorama of initiatives related to the modernization of legacy systems based on MSA. This panorama enables us to understand the following aspects:
* A taxonomy of the initiatives identified in the literature. In light of our investigation, this taxonomy compiles the principal evidence on the initiatives identified in the literature. In summary, this taxonomy can serve as a theoretical framework and a source of valuable insights, thereby facilitating the design of new initiatives. * The application domains that needed to modernize their systems based on MSA. The evidence presented here can provide insights related to the features that are required by such initiatives, which may vary depending on the domain or subdomain in question. * The correlation between the evaluation strategies employed by these initiatives and their level of maturity. Our study found that more rigorous evaluation tends to improve the credibility of an initiative and increase its adoption by the organizations. * The most common quality attributes. The results of our investigation revealed the advantages of implementing monitoring systems for modernized software, specifically in the context of microservices. * The main activities related to modernization. The discovered process has the potential to serve as a guideline framework for guiding different stakeholders in the activity of modernizing a legacy system with the implementation of MSA, taking into account the diverse organizational structures and technological architectures that may be involved. Furthermore, our findings show that the proposed process has the potential to be customized and instantiated to serve other application domains.