Skip to content

Recommendation System — Notes#

Functional#

  • Personalized rankings of items.
  • Real-time signal consumption.
  • A/B experiment slots.
  • Cold start handling.
  • Safety / business policy.

Non-functional#

  • p99 < 100 ms for rank stage.
  • 100M+ items, 1B+ users.

Trade-offs#

  • Collaborative vs content-based vs hybrid: hybrid wins for big platforms.
  • Online vs offline training cadence: real-time for recs of fast-changing inventory.
  • Explainability: hard for DNN; keep simple ranker fallback.

Refs#

  • "Deep Neural Networks for YouTube Recommendations" (Covington et al.).
  • Pinterest PinSage; LinkedIn People You May Know.
  • TikTok's "Monolith".