TokuDB is a replacement storage engine for MySQL that used fractal trees.
Tokutek was the original company building TokuDB. They were acquired by Percona in 2015
Relational
http://www.tokutek.com/products/tokudb-for-mysql/
https://github.com/percona/tokudb-engine
@tokutek
Percona
US
2009
Commercial, Open Source
MySQL
GPL v2
https://en.wikipedia.org/wiki/TokuDB