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Semicolony ELI5 · comic

Bloom filters.

A bouncer’s “definitely not on the list” memory: tiny, fast, and never wrongly says no.

  1. All of it? No way.
    1

    A full guest list is huge — too big to carry or check quickly.

  2. just a few bits 000000
    2

    Keep a tiny grid of on/off switches instead — a few bits, not the whole book.

  3. "bit" stamps → 101001
    3

    To add a name, run it through a few stamps and flip those switches on.

  4. Not on the list.
    check "zed" 101 a 0 → definitely not in
    4

    To check: stamp the name. Any switch off? It was definitely never added.

  5. check "ben" 111 all 1 → maybe (could collide)
    5

    All switches on? It is probably in — but switches can collide, so “maybe.”

  6. 101 skip slow disk
    6

    Tiny and fast, never a false “no” — perfect for skipping expensive lookups.

A few bits and a few stamps stand in for a list too big to carry.
Semicolony semicolony.dev/eli5/bloom-filter/comic
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