HLD-219·Storage & Caching
Medium · 1,000 ptsCollaborative Music Playlist & Synced Lyrics Store
Design a music streaming playlist and time-synced lyrics backend serving album-drop surges while immediately reflecting track additions in shared playlists.
Max p99
≤ 42 ms
Availability
≥ 99.5%
Budget
≤ $4,900
Functional Requirements
- FR-1GET /playlists/{playlist_id} — Fetches ordered track list and time-synced lyric frames.
- FR-2POST /playlists/{playlist_id}/tracks — Appends tracks to a collaborative playlist.
- FR-3PUT & DELETE /playlists/{playlist_id}/tracks/{track_id} — Reorders or removes tracks and immediately updates collaborator caches.
- FR-4Playlist edits must immediately appear to collaborators (read-after-write) despite 6x storage brownouts.
Workload Profile
Baseline Streaming40,000 Read RPS / 3,500 Playlist Write RPS
Midnight Album Drop118,000 Read RPS / 10,000 Write RPS
Active Working Set28 GB hot playlists & synced lyric payloads
Traffic DistributionHeavy Zipfian skew on featured editorial playlist_id keys
Consistency Model
Read-after-write consistency required on playlist mutations; circuit breakers protect against storage brownouts.
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