Slightly off topic, but I notice a lot of "full stack" courses on Udemy all use Mongo as their backend. Yet, I've always heard (hearsay) that Mongo licensing and reliability are bad. Are there not established training and "stacks" that utilize, say, Cockroach or Postgres, or some other NoSQL? Clearly I could swap out db layer with some work; I'm just surprised that training seems to focus on a database so reviled on HN.