Since it's in private beta which started a few weeks ago there is not specific system in production of Sub0 specifically, but someone (medical research institute with lots of research data) is already building a React frontend over their massive Postgres database using Sub0 and so far it's going well. The tutorial i provide explains building a complete API for something like Trello At the core of the system sits PostgREST and you can see a few users here http://postgrest.com/en/v0.4/intro.html#in-production although i suspect a lot more people are using it but don't advertise it. I've also done extensive performance test for speed, those numbers on the home page are real :)