Percona provides a patched version of MySQL with many enhancements. I believe they incorporation many of the useful community patches, such as from Google, and some of their own to make InnoDB function better on SSDs, etc (at least that was the case in the past, many of those may have made it into mainline MySQL now). They also provide their own storage engine, XtraDB, with it's own set of interesting features.

Additionally, they provide a set of utilities as the percona toolkit to automate more advanced things, such as replication testing through table data checksums, zero-downtime table changes, etc.

Most of it is free, I think some advanced XtraDB features require payment (?), but they sell support and training.

Percona offer best-in-class support for MySQL.

Tokutek make a database engine. They offer it in two versions-

• One version (TokuDB) which runs inside MySQL (Alongside InnoDB/XtraDB, MyISAM, etc).

• One version (TokuMX) which runs in/as a fork of MongoDB. Since Mongo didn't historically use plugable storage engines, they had to fork the MongoDB code in order to use their storage engine.

Their engine has some advantages over the traditional Mongo storage engine (Now called MMAPv1) - One of the most prominent was that it supported in-line compression.

Many of these advantages are mitigated somewhat by MongoDB's new WiredTiger engine.

Tokutek provides an "engine" for MySQL. Each table in MySQL has associated with it a engine that does the storing and retreaval. Like all software it's optimized for certain use cases. Tokutek used a fractal tree index to allow faster lookups. I think they could reindex a table without locking .

They more recently did an engine for mongodb A description from the Boston MySQL group a few years back (I was at the talk:)

http://www.tokutek.com/2012/01/fractal-tree-indexes-and-mead...

> some all-caps text

The section titles are capitalized. Come on.