Good point. MongoDB scales horizontally (add more servers) PostgreSQL scales vertically (get a bigger server) which is the least desirable way to scale, in addition to be being reliant on fewer servers makes it less fault tolerant. MongoDB is also schema-less which is convenient for developers and makes change management easier , but the cost is your app has an undocumented and unrestricted data model that only your core devs can partially explain, and your business analysts absolutely hate anything that isn’t standard SQL. So the story with MongoDB is core app devs still love it, operations is OK with it, and for everyone else you better copy that biz data into something that speaks standard SQL or the analysts will riot.