Is MongoDB the leader in NoSQL? I stopped using them years ago because of scaling issues. With things like Elastic Search and Dynamo DB, I see no reason to use MongoDB anymore.
It depends on whether you need it to be free as in free beer.
Couchbase is an enterprise grade NoSQL database, it scales very well, and it has a full SQL-like query language, and a lot of large companies use it.
The community edition is free as in free beer and it is also open source. For enterprise use, you can buy a support contract, and there is an enterprise edition.
There are many types of databases and MongoDB remains one of the top choices for document-stores. "NoSQL" is a meaningless term and is yet another point underscoring how better marketing always wins.
Elasticsearch is a cool search engine and really excels at some workloads that mostly fall into the realm of analytics and search, but it has its own set of very strict limitations (for example it sucks at updates, cannot do proper joins,...) which make it of limited suitability as a general purpose data store.
Well, it does say "reallyhyped.com" not "reallyused.com".
Joking aside, SQLite is on a ton of devices, yes. But that's primarily because it ships with OS's and is in lots of embedded devices. For web development and other server-side things, I get the feeling that SQLite is not as heavily used as client-server databases.
