What Mongo did is implementing these features just well enough so they can put checkpoint in their marketing brochures.
When you actually start using it you learn that most of it is either performing slow, does not work correctly or once in a while corrupts your data.
Yes they hit these points hard, but only from marketing point of view. They are now universally hated by ops and developers because these people now have to deal with fallout.
RethinkDB actually is an example that database is something that's not good as a base for a startup[1], and the Open Source approach (like PostgrSQL) is more suitable.
MongoDB is example that you can base a startup on a database technology and succeed, if you can sleep well at night that your product can cause people to lose data.
[1] The reason RethinkDB failed was because they refused to provide half solutions like MongoDB, everyone expects startup to start making money, but building a reliable databases is not something that's easy and can't be done quickly.
MongoDB serviced one of my projects for 5 years without a single hitch. It did everything I wanted it to do, it did it well, it did it exactly as advertised (no more, no less), and it did it right when I needed it. It never stopped improving during those years, massively in some aspects. The company behind it only grew stronger during those years, and along with it, so did my confidence that my project wouldn't need to undergo re-engineering further down the line.
Seriously, as a professional software developer, what more do you want.
Secondly, it’s the ReQL. It’s not native but not JSON based either. A weird hybrid mix.
But it’s only my personal opinion based on my taste.
> A RethinkDB employee told me he thought I was their biggest user in terms of how hard I was pushing RethinkDB.
http://blog.sagemath.com/2017/02/09/rethinkdb-vs-postgres.ht...
As much as I'd love this to be true, the #1 measure of success is if people even know you exist and #2 is if you solve enough of a customer's problems that it's worth using your product. MongoDB hit these two points hard right out of the gate and are now very successful because of it.