System design interview question
Design a Real-Time Feed Ranking System for a Social Media Platform (10M DAU, 500M feed impressions/day)
Design a distributed system that ranks and serves personalized feeds for a social media platform with 10 million daily active users generating 500 million feed impressions per day across multiple geographies. Users follow 100-1000 accounts each, and the system must deliver ranked feeds within 200ms p99 latency while handling real-time events (new posts, likes, comments). The ranking algorithm considers user engagement history, social graph proximity, content freshness, and collaborative signals. The platform operates across 3 regions with peak traffic of 100K requests/second during primetime. Design the complete pipeline including data ingestion, ranking computation, caching strategy, storage architecture, and real-time feed serving while maintaining consistency and handling failures gracefully.
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