Design TikTok's For You Feed
HardSystem design · Short Video Ranking · TikTok
Design TikTok's For You feed. Creators upload short videos (transcoded and moderated before wide distribution); ~700M daily viewers get an endless, personalised feed with no follow graph required; watch and skip events feed back into ranking within seconds. Cover candidate retrieval and ranking, cold-start exposure for new videos, online features, prefetch/playback latency, and feedback loops. Out of scope: the ads system, creator monetisation, and in-depth video codec design.
Requirements
- Support upload, transcoding, moderation, and global video delivery
- Rank candidate videos using user features, video features, and recent engagement
- Collect high-volume watch events for feedback loops
- Discuss candidate generation, ranking, caches, online features, and exploration