Monolith or Microservices or Both

Robert Grandl

May 16, 2023

How to write distributed applications has been a long-standing and highly contentious topic. Proponents of microservices argue that breaking down an application into microservices brings benefits such as improved scalability, independent deployment, and easier maintenance. On the other hand, supporters of monolithic architecture argue that a single, cohesive system promotes simplicity, easier development, and reduced operational overhead. This heated debate reflects the diverse needs and perspectives of different teams as they strive to find the most suitable architectural approach for their specific projects.

We have written a vision paper that will appear at HotOS'2023, in which we describe our vision on how to write distributed applications. We argue that developers should write their application as a modular binary and decide later whether they really need to move to a microservices-based architecture. By postponing the decision of how exactly to split into different microservices, it allows them to write fewer and better microservices. We believe that this approach eases the tension between the two different architectures, allowing developers to achieve the best of both worlds.

When writing a distributed application, conventional wisdom says to split your application into separate services that can be rolled out independently. This approach is well intentioned, but a microservices-based architecture like this often backfires, introducing challenges that counteract the benefits the architecture tries to achieve. Fundamentally, this is because microservices conflate logical boundaries (how code is written) with physical boundaries (how code is deployed). In this paper, we propose a different programming methodology that decouples the two in order to solve these challenges. With our approach, developers write their applications as logical monoliths, offload the decisions of how to distribute and run applications to an automated runtime, and deploy applications atomically. Our prototype implementation reduces application latency by up to 15× and reduces cost by up to 9× compared to the status quo.

Looking forward to an interesting discussion at HotOS'23 about microservices versus monolithic architectures.