System design newsfeed
Feed — push vs pull
Fan-out on write vs read. Hybrid for celebrities. Draw both paths.
Week 4Saturday 7 NovemberNewsfeed
Day 26: Newsfeed
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System design newsfeed
Ranking, fan-out, celebrities
Precompute vs rank-at-read. Cache the first page. Invalidate on mute/block.
Estimation
Fan-out for 10M DAU
100 follows, 5 posts/user/day. Writes if you fan-out on write. Storage of timelines.
Coding design
Design Twitter
LC 355. In-memory. Merge-k latest tweets. Then say what production adds.