Search and analyze your data in real time.
When you really need a database that can be used to search for data, I would recommend Elastic Search. It's a good database if you have eg. webshop where your products can be searched quickly or you need to late the users search in your content.
I've tested both MySQL and MongoDB at this point. MySQL gets too slow when you search in it if you have too much data to search. MongoDB is fast enough if you its okay for the user to have a wating time on 1-2 sec, but is You're looking for a relly fast search engine then Elastic Search is clearly the database you need to look a little more on.
I use Elastich Search on my work where one of the big problems has been to be able to search for 250,000+ products fast enough and still as close to real time data as possible, After we use Elastic Search that have solve our task.