How Bloom Filters Store 100 Million Items in 120 MB While Never Missing a Match
In 1970, Burton Howard Bloom faced a problem that would feel familiar to any modern software engineer working with large datasets. He needed to check whether words required special hyphenation rules, but storing 500,000 dictionary entries in memory was prohibitively expensive. His solution—a data structure that uses dramatically less space than any traditional approach—became one of the most widely deployed probabilistic data structures in computing history. The insight was radical: what if you could trade certainty for space? A Bloom filter will never tell you an item is absent when it’s actually present (no false negatives), but it might occasionally claim an item exists when it doesn’t (false positives). For many applications, this trade-off is not just acceptable—it’s transformative. ...