Would like to have an app with multiple micro apps each with their own set of models and config file etc. Curious how anyone would consider allowing them to communicate. I could do a curl call between them for they are simple REST apps, but would like some way for them to talk without extra requests.
If they are all on the same server you could have a common session component for all to avoid logging in each one
Direct pipe communication is always faster. But less scalable solution for sure.
So standard HTTP(S) communication is the way to go if you want to have scalable micro services architecture.
Of course there are more efficient ways than HTTP, but that largely depends what is your goal.
In enterprise design architecture we introduce MQ (message broker) service then.
Full duplex TCP persistent connection will be always faster, if your goal is top performance app.