I control-F'ed and didn't find it before I wrote that comment. I searched for KDB and APL, but found nothing.

EDIT: yeah that sentence is new. I think some of the sentences around Influx being the "first" have been adjusted too now saying it is the first "mainstream" and called other db's niche. it's also a little off. KDB+ is more popular in large banks and trading firms than HFT places.