I built a project that supported my PhD in Meteor.

My memory of it is that Meteor is fantastic, but Mongo is a nightmare.

I spent hours carefully designing my database so I didn't need joins and adding indexing, but it never ran as fast as unoptimised MySQL, and had vastly less functionality.

Mongo was literally all hype - I find it impossible to imagine the use case. A salutary lesson in how rubbish the latest fashionable thing can be.