🐦Twitter / X Feed
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Twitter / X Feed
● Intermediate30–45 min
Problem
Build the home timeline service for a social platform like Twitter/X. When a user posts a tweet it must be delivered to all followers' home timelines. Celebrities with millions of followers require a hybrid strategy — pre-computing timelines for everyone would create massive write amplification.
Functional Requirements
- Post a tweet → appears in followers' home timelines
- Load home timeline (last 200 tweets from followed accounts)
- Hybrid fan-out: push for regular users, pull-on-read for celebrities (>1M followers)
- Follow/unfollow with immediate timeline effect
- Mention and reply notifications
Non-Functional
- 300M DAU, 500M tweets per day
- Timeline load < 100 ms at p99
- 99.99% availability — read path must never go down
- Fan-out for normal users complete within 5 seconds
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Design your Twitter / X Feed
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UML
15
Needs Work
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Speed
RPS
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