There are many derivatives of MySQL.
Two popular ones are MariaDB and Percona.
MariaDB is an alternative database management system (or DBMS) which began life as a fork from the MySQL project.
MariaDB is significant because it is driven by the original designers of MySQL.
The guys forked away from MySQL in 2009 and founded the MariaDB Foundation because of worries over the future development of MySQL following its purchase by Oracle.
You can discover more about the history of MariaDB at the following link.
Why consider MariaDB instead of MySQL for Joomla?
An interesting question considered by a fellow Joomler who reports in his blog post (see link below) that he observed a 5% improvment in database query speed when he installed his Joomla! website on a server running MariaDB.
For our own part, we discovered MariaDB by chance when migrating a customer website from one server to another.
The website performs much better in its new home and this may in part be a function of the new server environment using MariaDB.
The Joomla! Project does not officially recommend using MariaDB on its Technical Requirements page.
But Joomla! performs very well on servers running MariaDB.
There are currently several versions in use.
Visit the following link to see if your website is using the latest available release.
Percona is another MySQL derivative.