TikTok's For You Page is the model recommendation system of 2020s. Watch time + engagement → immediate feedback → next-video ranked. Global scale.
Short feedback loop
Watch time per video = instant signal. Skip = negative. Like/share = positive. Model updates in near-real-time.
Short feedback loop
Watch time per video = instant signal. Skip = negative. Like/share = positive. Model updates in near-real-time.
Real-time feature store
User's recent interactions available within 1 minute for next request. Fresh signals matter for short videos.
Candidate → fine → rerank
Candidate gen recalls 1000s. Fine ranker (DNN) scores. Rerank ensures diversity + prevents repetition.
Model updates continuously
Not batch retrain. Streaming updates to embeddings + parameters. Emerging trends captured within hours.
A/B at massive scale
Thousands of experiments running simultaneously. Small user cohorts test model variants. Winners rolled out.