A few years back I used to store user data in the URL in conjunction with the goo.gl API (now deprecated), sort of a hack but worked great as a serverless key value storage, used it at fretflip.com to create shareable fretboard charts for guitar.
https://www.fretflip.com | An interactive guitar fretboard tool to make shareable scale and chord charts. I'm using it as a common place for learning guitar and bass. Opened it up for others to store their own charts, some are using it for education. Still non-profit but glad to share.