I currently have a monolithic server application that provides some workforce management workflow features. This monolith is getting unwieldy, and I'd like to split it up and make it more modular. I'm thinking about potentially creating microservice containers on Kubernetes, but I also like the idea of using a microkernel plugin architecture so that the core platform doesn't have to hard-code every feature. A Pub/Sub event bus helps with some of that, but I also need to be able to make direct invocation calls (e.g., REST or gRPC) in some of the workflows.

Are there any effective patterns which combine the microservice pattern with the microkernel plugin pattern? Perhaps maybe using configuration files to define various workflow hooks?