Signal Multiple Workflow Executions

I have a use case where multiple workflows are waiting on a single state change outside of the workflows. What is the best way to communicate to all all of the workflows that the state change complete and to continue to process? Is there a simple way to send signals to multiple workflow executions?

We were looking into doing something similar lately and seems like there is a way to do this using batch operations, however I wasn’t able to find something similar in java sdk. One other way to do the same is by sending a post request to temporal open api endpoint (/openapi) if your temporal cluster has one:

You should be able to get more info from here Protocol Documentation

What is the expected fan out? And how do you identify workflows to signal?