Evolving legacy enterprise systems into a lean system architecture has been on the agendas of many enterprises. Recent advance in legacy system evaluation is in favour of microservice technologies, which not only significantly reduce the complexity in deployment of enterprise systems but also enhance the availability of services to system users. However, there are technical challenges to overcome towards a successful transformation. Challenges, relating to information security, container optimisation, the performance of a new system and its deployment, are particularly under concern. To cope with these technical challenges, a new approach is proposed in this paper to govern the evolution of legacy systems into a microservice-based and cloud-hosted architecture. This approach includes a detailed working process, a set of transformation rules towards microservices and their repositories. In addition, a conceptual framework is drawn to provide a comprehensive illustration to this evolution approach. Moreover, a case study is presented to demonstrate the application of the proposed approach on the evaluation of a chosen legacy system, as well as the procedure of system architecture optimisation.

Evolution has always been a challenge for enterprise computing systems. The microservice based architecture is a new design model which is rapidly becoming one of the most effective means to re-architect legacy enterprise systems and to reengineer them into new modern systems at a relatively low cost. This architectural style has evolved based on a number of different approaches and standards. However, there are quite a few technical challenges which emerge when adopting microservices to revive a legacy enterprise system. In this paper, an evolution framework and a set of feature-driven microservices-oriented evolution rules have been proposed and applied to modernise legacy enterprise systems, with a special emphasis on analysing the implications as regards runtime performance, scalability, maintainability and testability. Testing and evaluation have been carried out in depth, aiming to provide a guidance for the evolution of legacy enterprise systems.