Social News Feed (FB News Feed)
Difficulty: Medium
What It Tests
Feed ranking, fan-out at scale, read-heavy optimization.
Topics Covered
- Fanout Patterns
- Caching
- Message Queues & Async Processing
- Database Design: SQL vs NoSQL
- Database Replication
- Redis Deep Dive
Hello Interview Breakdown
Read the full Hello Interview breakdown →
Approach Hints
- Fan-out-on-write for regular users (push posts to follower feed lists in Redis sorted set)
- Fan-out-on-read for celebrities
- Rank feed by a score (recency + engagement)
- Serve cached feeds from Redis for active users