The microservices architecture is one of the first service-based architectural styles that has been introduced, applied in practice, and become popular when the DevOps practices gained momentum in the software industry. Migrating monolithic architectures to cloud-native architectures like microservices brings in many benefits such as flexibility to adapt to the technological changes and independent resource management for different system components. Here, we report our experiences and lessons learned during incremental migration and architectural refactoring of a commercial Mobile Backend as a Service to microservices. We provide a detailed explanation of how we adopted DevOps and its practices, and how these practices facilitated a smooth migration process. Furthermore, we have taken a step towards devising microservices migration patterns by wrapping our experiences in different projects into reusable migration practices.

Abstract. Migration to the cloud has been a popular topic in industry and academia in recent years. Despite many benefits that the cloud presents, such as high availability and scalability, most of the on-premise application architectures are not ready to fully exploit the benefits of this environment, and adapting them to this environment is a non-trivial task. Microservices have appeared recently as novel architectural styles that are native to the cloud. These cloud-native architectures can facilitate migrating on-premise architectures to fully benefit from the cloud environments because non-functional attributes, like scalability, are inherent in this style. The existing approaches on cloud migration does not mostly consider cloud-native architectures as their first-class citizens. As a result, the final product may not meet its primary drivers for migration. In this paper, we intend to report our experience and lessons learned in an ongoing project on migrating a monolithic on-premise software architecture to microservices. We concluded that microservices is not a one-fit-all solution as it introduces new complexities to the system, and many factors, such as distribution complexities, should be considered before adopting this style. However, if adopted in a context that needs high flexibility in terms of scalability and availability, it can deliver its promised benefits.

Summary Microservices architectures are becoming the defacto standard for building continuously deployed systems. At the same time, there is a substantial growth in the demand for migrating on‐premise legacy applications to the cloud. In this context, organizations tend to migrate their traditional architectures into cloud‐native architectures using microservices. This article reports a set of migration and rearchitecting design patterns that we have empirically identified and collected from industrial‐scale software migration projects. These migration patterns can help information technology organizations plan their migration projects toward microservices more efficiently and effectively. In addition, the proposed patterns facilitate the definition of migration plans by pattern composition. Qualitative empirical research is used to evaluate the validity of the proposed patterns. Our findings suggest that the proposed patterns are evident in other architectural refactoring and migration projects and strong candidates for effective patterns in system migrations.

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