Just found this out, didn’t know that command existed.
$ kbdrate -r30 -d0
This sets the repeat rate to 30 characters per second (which is the maximum value) and a repeat delay of 250 ms (which is the lowest possible).
You may sometimes notice your keyboard rate/repeat delay is slow after attaching it to a running system which was booted without a keyboard attached. I guess this command would help. No guarantee on that though.