I dunno man, I think Kx deals with out of memory data in the most sane way imaginable if you assume time oriented problems and understand how computers work (aka latencies in squirting the data across different layers of hardware into the CPU). I have no idea what they're giving people for manuals for setting up for different query patterns these days, but the old K3 manuals were great; classics of database engineering and practical computer science. Petabytes before it was routine.
The APL family takes some getting used to, as it's a significantly different paradigm from Julia and Python looking languages: arguably as different a paradigm as Lisp. It's also fairly natural if you've done any work with Matlab, NumPy or other array oriented packages, but you do have to put in the work.
It doesn't get as much attention here, but Jd is pretty good also. It's also much lower barrier to entry than Kx if you're building a personal project with it (aka its free for personal use). J is a more complex language than K, but I like it better; more oriented towards mathematics.
The APL family takes some getting used to, as it's a significantly different paradigm from Julia and Python looking languages: arguably as different a paradigm as Lisp. It's also fairly natural if you've done any work with Matlab, NumPy or other array oriented packages, but you do have to put in the work.
It doesn't get as much attention here, but Jd is pretty good also. It's also much lower barrier to entry than Kx if you're building a personal project with it (aka its free for personal use). J is a more complex language than K, but I like it better; more oriented towards mathematics.
https://code.jsoftware.com/wiki/Jd/Overview