Your question is URL Shortener System Design. Take a moment with it on the right.
Talk me through your thinking if you like. When you're confident, submit your answer and I'll grade it like a real screen (7/10 or better passes).
Design and explain a URL shortener service, including key components and trade-offs.
Explain the API and request flow for creating short URLs and redirecting users. Cover identifier generation, persistence, collision avoidance, expiration, abuse controls, caching, availability, and observability. Make reasonable assumptions explicit, and discuss how your design would change as traffic, storage volume, or reliability requirements increase.