best way to store players data

i'm making a plugin that saves all players settings money and stuff so i was wondering what is the best and fastest way to store data
..sorry for my bad english

 

RAM

 

That may be the fastest but not the best. If your keeping the data you should use a database such as MySQL or MongoDB.

 

I'd go with MySQL as well. SQL tables are usually great in this aspect.
Its not the fastest when you're fetching/updating small data but that's where asynchronization covers it up, but works amazingly well with large data. For example: fetching the top 10 players with the highest money value - usually takes a few milliseconds for a table consisting of 100k entries.
Since you're making a plugin that I assume is going to be public, many might find it annoying to set up a MySQL server just to use the plugin. So there's always SQLite which is a flat file version of MySQL in a very vague sense.
If you're ever going to make a website displaying the top 10 players, all you need to do with MySQL is connect to MySQL server and run your query, so there's an advantage of extendability.