System Design
Advanced
Design a Social News Feed
Design feed generation for regular users, celebrities, ranking, freshness, and read latency.
40 min
3 sections
feed
ranking
fanout
1
2
3
01. Compare fanout strategies
Section 1 of 3
Fanout-on-write precomputes feed entries when someone posts. Fanout-on-read computes the feed when a user opens it. Large systems often use a hybrid: push normal authors and pull celebrity or high-volume authors.
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Hybrid feed:
- Regular author post: write post_id into follower inboxes.
- Celebrity post: store in author outbox only.
- Feed read: merge user inbox + celebrity outboxes + ads + recommendations.
- Rank: apply freshness, engagement, relationship strength, and blocks.Back to Course