From the Salesforce Heroku Team: Extend Flows with Heroku Compute and External Services

This detailed blog post from Salesforce shows how to use a specification created using the Open API Spec to generate Flow Action via External Services. So far, that’s not really new. But then the authors show how you can create a Heroku-based implementation of that API using Node.js. Finally, they show how platform events can be used to communicate effectively from Heroku back to a triggered flow.

Check it out.