A large online game like World of EverCraft can benefit from using a Bloom filter to efficiently check for the existence of usernames without having to query the entire database, instead relying on probabilistic data structures that offer faster and smaller data structures in exchange for some uncertainty. By controlling the error rate and bit width, users can mitigate this uncertainty and gain performance and compactness at the cost of limited accuracy. The Bloom filter implementation is surprisingly easy to understand and implement, with an array of bits used to store indices generated by hashing functions applied to user input, allowing for fast lookups and insertions while minimizing memory usage.