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The Social Feed

A home feed for a hundred million users: where a timeline lives, how it is ranked inside a latency budget, what the celebrity accounts do to the write path, and the whole design under a viral hour.

Lessons
5
Exercises
29
Minutes
34

Start Where a Timeline Lives

  1. 1

    Where a Timeline Lives

    After this lesson you can size a per-user timeline store, choose its shape and cap, and say why it holds ids rather than posts.

    DebugMultiple choiceShort answer
    5 exercises
    6 min
  2. 2

    Ranking Inside a Latency Budget

    After this lesson you can lay out a candidate-score-rank pipeline that fits a feed's latency budget, and say what is precomputed and what is computed per request.

    DebugCode orderMultiple choiceShort answer
    5 exercises
    6 min
  3. 3

    Celebrities, Follows and Unfollows

    After this lesson you can handle the accounts above the fan-out threshold end to end, and keep timelines right when a user follows or unfollows.

    DebugMultiple choiceShort answer
    5 exercises
    6 min
  4. 4

    Checkpoint: Feed VariationsCheckpoint

    The same design under different numbers: a workplace feed, a digest, and a feed with no celebrities.

    DebugMultiple choiceShort answer
    6 exercises
    6 min
  5. 5

    Boss: The Social FeedBoss

    The whole design: the question, the numbers, the stores, the write and read paths, the viral hour, the missing post, the revised pipeline, and the tradeoff you defend.

    Code orderMultiple choiceShort answerTrace
    8 exercises
    10 min