From Microservice to Monolith: A Multivocal Literature Review

Recently, the phenomenon of switching back from microservice to monolith has increased in frequency, leading to intense debate in the industry. In this paper, we conduct a multivocal literature review to investigate reasoning and key aspects to pay attention to when switching back and analyze other practitioners' opinions. The results show four cases of switching back from microservice to monolith: Istio control plane, Amazon Prime Video monitoring service, Segment, and InVision. The five main reasons that led to switching back are cost, complexity, scalability, performance, and organization. During the switching back process, six key aspects need to be addressed: (1) stopping the development of more services, (2) consolidating and testing paths, (3) unifying data storage, (4) implementing the message bus principle, (5) giving up diverse techniques, and (6) learning to use modular design principles. As to the practitioners' opinions, they had mixed views about the switching back phenomenon. However, most thought that switching back required consideration of the actual system situation and principles. These results pave the way for further research and guide researchers and companies through the process of switching back from microservice to monolith.