Facebook News Feed System Design
System design for Facebook News Feed with fan-out on write architecture. Post Service writes to DynamoDB, triggers Fanout Worker to pre-compute feeds into Redis cache per user. Follow Service manages uni-directional relationships. Feed Service reads from pre-computed cache for low-latency feed delivery.
facebooknews feedsystem designfan-outdynamodb
Requirements
Functional
- Create posts with rich content
- Follow/unfollow other users
- View chronological feed from followed users
- Page through feed with cursor-based pagination
Non-Functional
- Highly available (availability over consistency)
- Feed loads in under 200ms
- Tolerate up to 1 minute post staleness
- Scale to billions of users and posts
Author
Published
February 17, 2026
Last updated February 18, 2026