Ever wondered how apps check if a username is available, almost instantly, even with billions of users? 🔎 They use something called a Bloom Filter: a smart, space-efficient data structure that can quickly tell if a username is probably taken or definitely available, without searching every single entry. Here’s the trade-off: Bloom Filters can sometimes give a false positive (saying a name is taken when it’s not), but they never miss a real match. It’s a great example of how computer science sol