If you look at the reactive architecture as a standardized approach, you won't find a guide or rules for how to turn your microservice reactive, but there is The Reactive Manifesto, which you can find here: https://www.reactivemanifesto.org/. It contains a list of principles you can use to be inspired by ideas for the improvement of your application.

Now we can create an example of a reactive microservice for the JSON-RPC procotol.