Consistency and Availability in Microservice Architectures

For the most part, the first instances of microservice architectures have been deployed for the benefit of the so-called Internet-scale companies in contexts where availability is a critical concern. Their success in this context, along with their promise to be more agile than competing solutions in adapting to changing needs, soon attracted the interest of very diverse classes of business domains characterized by different priorities with respect to non-functional requirements. Microservices embraced this challenge, showing a unique ability to allow for a plethora of solutions, enabling developers to reach the trade-off between consistency and availability that better suits their needs. From a design point of view this translates into a vast solution space. While this can be perceived as an opportunity to enjoy greater freedom with respect to other architectural styles it also means that finding the best solution for the problem at hand can be complex and it is easier to incur in errors that can put a whole project at risk. In this paper we review some possible solutions to address common problems that arise when adopting microservices and we present strategies to address consistency and availability; we also discuss the impact these strategies have on the design space.