First, thanks. I honestly had never heard that description before. I definitely see it making more sense than the alternative interpretation of the phrase if you approach the concept of Karma as an actual metaphysical phenomenon rather than as more of a meme, as I think people often do.

That said, any time I've seen the phrase "instant karma" used, it's in response to something that occurs within seconds or minutes of what earned it, or "instant" in a more commonly used sense.