Bloom Filter
A Bloom filter is a space-efficient probabilistic data structure used to test whether an element is a member of a set. It can return false positives (indicating an element is in the set when it is not) but never false negatives (it will always correctly identify elements that are in the set). This makes it ideal for applications where memory is limited and occasional false positives are acceptable, such as caching, spell checking, or network routing.
Developers should learn Bloom filters when building systems that require fast membership queries with minimal memory usage, especially in distributed systems, databases, or web applications. They are particularly useful for reducing expensive disk or network I/O by quickly filtering out non-existent items, as seen in content delivery networks (CDNs) for cache lookups or in databases to avoid unnecessary queries. For example, in a web crawler, a Bloom filter can efficiently check if a URL has already been visited without storing the entire list.