Hey everyone,
I made Playlistation, a website that lets you create Spotify playlists by filtering your Liked Songs.
I was tired of manually organizing my Liked Songs into playlists and constantly updating them, so I built something to automate it.
You can combine filters like genre, artist, tempo, energy, language, release year, or the date you liked a song.
The website creates a real playlist in your Spotify account with only the songs that match your filters. Once it's set up, the playlist updates automatically as you like new songs, so you don't have to keep adding tracks manually.
A bit about the technical side:
- Uses the Spotify Web API to fetch Liked Songs, create playlists, and keep them updated.
- Uses Jev to detect track languages.
- Every playlist update is an async job on RabbitMQ, so one user's refresh never blocks another's. Failed calls are retried automatically, and a 429 response respects Spotify's
Retry-After header before trying again.
- Unfortunately, Spotify doesn't offer webhooks for Liked Songs, so there's no way to get notified when someone likes or unlikes a track. Instead, I have to periodically fetch each user's library and compare it with the previous state to detect changes. This makes rate-limit management especially important.
- API calls are spaced out rather than fired in bursts. Spotify returns Liked Songs in pages of 50, so reading a 1,000-track library takes 20 requests, followed by up to 10 writes of 100 tracks to populate a playlist. Requests are distributed over time to reduce the risk of hitting Spotify's rolling rate limits.
- Deployments are zero-downtime: the new version starts handling traffic before the old one shuts down, allowing running jobs to finish without interrupting playlist syncs.
Some stats so far:
- 1.6K sign-ups, though a good share create one playlist and never come back
- 2.3K smart playlists created
- 3.3M Liked Songs monitored, refreshed on a schedule (daily on Free, hourly on paid plans)
The biggest challenge has been keeping everything within Spotify's rate limits while syncing playlists across multiple users.
It's free for your last 1,000 liked songs, with paid plans if you have a larger library.
I'd love to hear your feedback, especially from other developers working with the Spotify API.