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Q35IntermediateSystem design

How would you use LLMs to improve a recommendation system for a content platform?

30-second answerSay your answer out loud first, then reveal.

Where LLMs add value

UseHowOnline/offline
Item enrichmentExtract topics, difficulty, entities from titles, descriptions, transcriptsOffline batch
Semantic item embeddingsBetter similarity for content-based retrievalOffline
Cold startRecommend new items based on content features before clicks existOffline features, online serving
User interest summariesSummarise long histories into interest profilesNear-line, periodic
Explanations"Recommended because you liked X"Online, small model or cached
Conversational discovery"Show me beginner-friendly RAG videos under 20 minutes"Online, separate flow
Final re-rankingLLM re-ranks top 20 for diversity or intentOnline, latency permitting

Architecture sketch: candidate generation (two-tower embeddings, collaborative filtering, LLM-based content embeddings) → ranking model (gradient-boosted or deep model with behavioural + LLM-derived features) → re-ranking/business rules (diversity, freshness) → optional LLM explanation.

Evaluation: offline (recall@k, NDCG on held-out interactions) plus online A/B tests (watch time, retention, diversity, satisfaction surveys).

Pitfalls: LLM-generated features may encode popularity or demographic biases; cost of enrichment at catalogue scale (use batch); explanations must be faithful to the actual reasons.

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