1010data indeed still uses K as a core language for its infrastructure, supplemented with some C libraries here and there. The internally-maintained fork of k3

1010data indeed still uses K as a core language for its infrastructure, supplemented with some C libraries here and there. The internally-maintained fork of k3 has grown some interesting features over the years, both unique and borrowed from newer K releases. I hear "Shakti" aka k7/k9 is used by a handful of cryptocoin exchanges. Their needs drove a number of design considerations in early k7, but I'm not up to date on k9. Most of the k4/kdb+/Q users I know work at hedge funds.