Some Research on In-Memory Database

So, I've been doing some research on in-memory database:

These URLs are of interest to me:
https://www.oracle.com/database/technologies/related/timesten.html
http://whatis.techtarget.com/definition/in-memory-database
http://www.voltdb.com/
https://apacheignite.readme.io/docs/
https://www.exasol.com/en/products/features-benefits/