Mood Music turns a mood or a line about your day into a handful of Spotify search phrases via Claude, then merges the results round-robin across phrases so the strongest hits from every phrase surface first. No traditional database — Workers KV handles sessions and 24-hour mood-search caching, and a per-user Durable Object holds OAuth tokens, search history, and the free-tier quota.
Read the full write-up in the linked post for the architecture, the free-tier design, and why it stays in Spotify’s Development Mode indefinitely.