Pega's new fnx project is still in relatively early (Microservice is part of that) but Pega teams are working relentlessly. I am not sure we have anything ready for external consumption yet. If you are interested in early adoption, I recommend engage your account manager and go from there.
if your requirement is about exposing some functionality as an API which can be consumed by the same app or different app from a different server also can be done if you could expose it as a Rest Service with your business functionality written in it.
please explain the requirement if you need more inputs to try/achieve the requirement.