Oh man, one question really stuck with me—it was during one of the technical interviews. The interviewer asked me to design a URL shortening service, like Bitly, but with a twist: it had to scale to billions of URLs and support custom aliases. At first, I was like, “Cool, I’ve seen this on system design prep lists,” but then they hit me with follow-ups about handling high availability, rate limiting, and eventual consistency across data centers. We dove into hashing strategies, database choices (SQL vs NoSQL), and cache layers using Redis. They asked how I’d prevent collisions and how I’d handle abuse—like people using the service for malicious links. It turned into a full-blown distributed systems discussion, and my brain was both thrilled and slightly melting. Easily the most fun (and most humbling) part of the interview.