If you're writing apps for user computers that have no reason to sync to a central remote database then SQLite is totally fine. If you're writing an application

If you're writing apps for user computers that have no reason to sync to a central remote database then SQLite is totally fine. If you're writing an application that runs in a cluster or on the web, Postgres is the way to go. There almost never a reason to go with Mongo unless you're just trying to get buzzwords in a presentation and trying to seem hip. That's going away now though. My place exclusively uses Postgres on all of our webservers.