Serveral apps in one DO Droplet

Hello! I read and understand how deploy several apps to one droplet. But i’m don’t understand, how i can separate MongoDB databases?
I working on service, wich create new subdomain with app for each user. Can you help me understand, how i can do this?

P.S. I’m sorry for my English, i’m from Belarus.

You can run multiple mongodb instances pretty easily. You just need to run them on different ports and have different folders/ configurations for them.
https://docs.mongodb.com/manual/administration/configuration/#run-multiple-database-instances-on-the-same-system

I am not completely sure about having separate subdomains (separate app) for each user. However, I think it would involve setting some kind of proxy. This package might help too https://github.com/mizzao/meteor-partitioner

I hope it helps.