Not disagreeing with you, just adding some color. We have a monolithic application (well, an application composed of many libraries that have a dependency tree

Not disagreeing with you, just adding some color. We have a monolithic application (well, an application composed of many libraries that have a dependency tree, but live in the same process) that contains individually deployable services that talk to one another over RPC. So when you're patching part of the codebase, you can deploy a branch to the servers that are executing the code you've just changed, thus no need to restart the whole thing. But you still have the benefits of shared libraries, moving functionality between services, collapsing service calls that are no longer performant, adding new calls temporarily, etc. In this model, you can introduce and remove service calls when it's useful, as opposed to as a result of how the code was put together. You will often do this for performance reasons, but just as often you'll do it for deployment flexibility. When you want to prototype something new, you can create a new service, branch the codebase, and have it talk to the rest of the infrastructure via service calls. When you're done you can keep it as a service, or, just as often, you can collapse the service back into other services so we don't have excessive RPC calls. When would we consider moving to services backed by different codebases? If our company were to grow so large that highly disparate teams would want to manage their own dependency trees--that's around when it makes sense to me to go microservice. (I not sure I'd call it microservices then, more SOA).