Where I work we use mongo, it's not what I would've picked but i guess it helped early dev speed and bad practices like having productus do direct db edits to save a situation because the app isn't mature yet.

By now when collections are getting huge and documents as well we've had to archive more and more recent data, which causes problems, and we have to really make sure our queries are sharp or cost and lag will go through the roof.

With that said, it actually works pretty ok for a production platform with quite a big customer base, and there are many improvements we could do if we had the time.

If I were there at day one I'd have rooted for sql, mainly based on how much these different collections have to relate, but I don't think mongo is as horrible as many people make it out to be and it does have upsides.