End-to-end Design

• Commerce
• Integrity Systems
• Search Engine
• Important Issues

Focus Areas

• Phase 1: Foundation Across Domains - Retrieval objective + index design - Item and user embedding modeling - Label shaping + feedback signal bias - Cold-start & tail item strategy

• Phase 2: Ranking Layer Design - Crossing techniques: concat, attention, deep crossing, FiLM - Personalization fusion: long-term vs short-term interests - Loss function trade-offs: point/pair/list/ordinal - Feature latency & stale signal impact

• Phase 3: Scaling + Infrastructure Trade-offs - ANN system design: PQ vs HNSW vs IVF - Embedding refresh frequency + tag injection - Multi-source hybrid retrieval + diversity injection - Shadow evaluation, drift detection

• Phase 4: Monitoring & Bias - Feature delay, bias amplification - Observability for ANN and ranking stages - Coverage/fairness audits, click model correction - Calibration, post-hoc re-ranking, threshold tuning