When should I use HyperLogLog instead of exact counting?
When cardinality is in the millions or higher and 1% error is tolerable. Real-world use cases: unique visitor tracking, deduplication streams, set intersection size estimation. Skip it for small sets where exact counts fit in memory.
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Count Billions in 12 KilobytesHyperLogLog estimates cardinality by reading leading zeros in hashed values, trading 1% error for fixed memory.
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