Mongo was so comically bad. I remember trying to sort through a slow query and thought: ah ha! I'll just add an index. Unfortunately on that version of Mongo, creating an index would occasionally just crash the server process.

I think Mongo became popular because it's ad tech and those guys knew how to be buzzword compliant. JSON-esque documents are one thing, but Mongo is Javascript to the core. All of a sudden your JS devs don't have to learn SQL they can just shit out some queries in javascript. Of course that came with some pretty severe drawbacks.

As I remember, MongoDB got popular before node.js, so there wasn't really a lot of backend JavaScript developers out there to make a difference.

We first used Mongo ~11 years ago with Java. For us the benefit was that we could dump unstructured data into it quickly, but still run queries / aggregations on it later.

My favourite story about MongoDB is that it was so bad and popular at the same time that when a competitor developed a wire-compatible database that was miles better they simply bought it and released it as the next version of MongoDB.

which db was that?

I think I meant WiredTiger.

This is true. And now MongoDB is miles better.