senior System design
Design a social media news feed
Design the system that powers a personalized timeline. Each user follows others; the home feed must be fresh, ranked, and personalized within hundreds of milliseconds.
Scale targets
Users: 1.5B DAUQPS: 5M feed pulls/secLatency: <300ms p99Storage: ~50PB total media
Key areas
Push vs pull vs hybrid fanoutRanking pipeline (candidate generation → ranking → re-ranking)Cold start for new usersCache hierarchy + edge deliveryMedia CDN + transcoding