It's fast because it doesn't actually save your data when you ask it to. It saves it later, when it feels like it, maybe. Also, the hate I have for Mongo is fro

It's fast because it doesn't actually save your data when you ask it to. It saves it later, when it feels like it, maybe. Also, the hate I have for Mongo is from first-hand experience with the wretched thing. The scaling is insane. The next jump after your first server is like 9 servers (2 repsets w/ 3 servers each w/ 3 config nodes). I don't have that kind of cash laying around for servers, especially when instance-for-instance, Postgres can handle easily 10x the write load of mongo.