After yelling at Alexa like a crazy person for the third or fourth time in one day, I figured something had to change. It was the same pattern every time. I'd say the wake word, give a command, get it ...
Messages was right at the top of the list with several gigabytes' worth of data. It easily eclipsed Spotify, which I know has a few gigabytes, because I've set it to cache music like my weightlifting ...