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Sub-counters

One counter split across several keys, summed on read, so writes spread out.

Taught in Chapter 30: Hot Keys.

More from the same chapter

• Fan-out on read: Building a feed when it's opened, from the latest posts of everyone followed.
• Fan-out on write: Copying each new post into every follower's feed when it's published.
• Hot key: One record that draws more traffic than one machine can serve.