I love streaming algorithms - they make you think! Since they can process data in (near) real-time, they are ideal for applications where immediate feedback is needed. Most of today's recommendation or machine learning systems are built on batch process, however.

No, we are not talking about Hash browns. 😗

In any system, there are millions and millions of users record. How could a system tells username is not available almost instantly. Enter Bloom Filter. 😎