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Semicolony ELI5 · comic

Sharding.

Splitting one giant phone book into A–M and N–Z so two people can search at once.

  1. My arms hurt.
    A–Z, all of it
    1

    One phone book has grown too thick and busy for a single person to handle.

  2. can’t grow forever
    2

    A bigger book only goes so far — eventually you can’t just buy a heavier one.

  3. A–M N–Z |
    3

    So you split it: A–M in one book, N–Z in another. Each slice holds part of the whole.

  4. A–M N–Z
    4

    A lookup goes straight to the right slice — and two people can now search in parallel.

  5. key hash spread evenly
    5

    Choosing the split is the whole game — keys are hashed so the load spreads evenly.

  6. Why is it all coming to me?!
    hot shard
    6

    Pick badly and one slice gets the celebrity account: a hot shard, swamped while the rest nap.

Splitting one giant phone book into A–M and N–Z so two people can search at once.
Semicolony semicolony.dev/eli5/sharding/comic
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