Like all technologies MongoDB is a tool and you need to pick the right tool for the right job or in this case the right DB for the right work load. We run 100's of TB of MongoDB with 100's of millions of Mongo Ops. Does it have challenges for sure, does mean you can't scale it no. Here's a talk about scaling MongoDB specifically. http://engineering.objectrocket.com/2014/03/10/scaling-mongo...