If you mean "free" as in open-source/free, there is J, which has its own builtin database. I'm assuming it's similar to k/kdb, but that's just a guess.

Learning an APL variant... not a free lunch. Takes a while and commitment to grasp.

J language is free, J database isn't - "Jd is a commercial database product from Jsoftware" - https://code.jsoftware.com/wiki/Jd/Overview

I've played with J and read a book on it. It's expressive and powerful of course, but wasn't nearly as natural to me as APL or Kdb+.

Arguably "crazy expensive" software that minimizes crazy expensive hardware is something work considering. Firms pay 10s of times more for things like DataDog than they do for a KDB+ license.

Also I found the argument that KDB+ devs are expensive to be laughable once I saw how much (same, or even more) we started to pay AWS/Python devs.

Crazy expensive may be affordable to firms like JP Morgan, but other industries just won't pay that when Postgres is free. It's not as good for the kind of analysis Kdb+ does IMO, but free is free and it's easier to just get a VM from IT.