I wonder if using the memcached plugin for InnoDB[1] would speed things up even more, at the expense of not having flexible queries (and thereby introducing multiple roundtrips) anymore. Presumably, they are using simple "SELECT * FROM table WHERE id = ?" in most places anyway, so that could be an okay tradeoff to make.

[1] https://dev.mysql.com/doc/refman/5.6/en/innodb-memcached.htm...