Another user of MongoDB here. Thus far it has scaled well for us where we had a similar situation where uptake was faster then expected. The WiredTiger storage engine made most of the concerns of 2012-2013 for MongoDB, non-issues. However, if you try to put a relational model in to MongoDB, you still may see performance issues down the road, but then again it should be about the right tool for the right job. I'd reiterate Ken Walger's post to checkout his blog, it does a great job of comparing MongoDB 2012 vs. MongoDB today. Also, if administration/operations are a concern, then cloud provided MongoDB is the way to go, MongoDB Atlas seems to be at the forefront since it's run by MongoDB itself. Good luck with your apps!