TL;DR — Spotify

Design a music streaming platform like Spotify that serves 500M+ users with instant playback, personalized discovery, and seamless offline sync. Unlike video streaming, audio files are small (3-10MB per track) but the interaction pattern is rapid — users skip tracks within seconds if the next song does not start instantly. Key features: Stream audio tracks with gapless playback between songs. Create, edit, and share playlists (up to 10,000 tracks).