they are using multiple cloud providers, but judging by the cloudflare r2 outage affecting them earlier this year I guess all of them are on the critical path?
not sure how interesting but definitely useful :D I like to listen to Albums and I missed the "Give me a random album from my collection" functionality in Spotify so built a tiny webapp to do exactly that - https://shuffle.ninja.
It uses the Spotify web APIs to fetch your album collection and gives back a random album from it. I use it daily.