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Problem Understanding
Restate the problem in your own words.
Design a News Feed (Facebook / LinkedIn)
Design a Facebook / LinkedIn-class news feed: each user opens the app and gets a ranked timeline of posts from people and pages they follow, blended with recommendations and ads. Reads dominate — every app launch hits the feed — and the recommender does most of the work. The hard parts are the feed mix (chronological + recommended + ads), the ranking pipeline, and serving 80M+ concurrent feed reads at sub-300 ms p95.
- Facebook News FeedThe canonical mixed feed — friends + pages + groups + ads, all ranked.
- LinkedIn FeedProfessional feed with a much heavier recommender than chronological component.
- Twitter Home TimelinePull/fan-out hybrid; the ‘For You’ tab is recommender-driven, ‘Following’ is chronological.
- Reddit /r/popularCommunity-mixed feed ranked by hot/score; same fan-out + ranking shape.
Your task: read the problem above, then write what the system is, who uses it, the rough scale, and the headline UX expectation — in your own words. Submit for AI review when you're ready.
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