EDIT: We'll just wait for Mongo to burn through all their cash then.
Mongo has a strong community, which translates into a plethora of articles/blog-posts/tutorials/etc that secures its niche. From there it's possible to make money with things like consulting fees to help fix the problems it created in the first place.
It's all about execution. Case and point: I know what (purportedly) makes MongoDB special. I have no idea what RethinkDB is supposed to do, other than store data. Yes, I could check their site, but the point is I'm already familiar with Mongo's reputation. All of this contributes to a lesser product winning over a better one.
Half the crap people speak about Mongo seems to be from either the early days, or from people who just like to complain. It certainly has it's issues, but there doesn't seem to be much community will to replace it with $superdupernosqldb.
Oh, yeah... and the ability to do shard + redundancy, where mongo you're either or have to do both. So scaling works a bit better. The admin tooling for rethink is better than anything I've really used in non-sql databases. And frankly even better than db admin tools, including sql based ones.
It's just a really great, stable database with really good scaling for the majority of use cases.
(sorry)
But please enlighten us poor fools which open source databases can compete with MongoDB in this space. It sure as hell isn't PostgreSQL.
I'm not a Windows fan, but that's harsh. http://cryto.net/~joepie91/blog/2015/07/19/why-you-should-ne...
Most of the the points are for issues that were fixed years ago and then you get classics like "forces the poor habit of implicit schemas in nearly all usecases" as if some developer is going to somehow stumble on the fact is it a schemaless database.
It's like trying to say "Linux is shit" because of issues found in 1.0 of the kernel.
https://objectrocket.com/blog/company/mongodb-wiredtiger
It's made a massive difference to performance and stability.
This is the JIRA tracking that Jepsen stale read issue: https://jira.mongodb.org/browse/SERVER-17975
