How would you design a URL shortening service? Please discuss the application architecture, database design, and any potential challenges.

## Approach Identify requirements such as scalability and security. Use a NoSQL database for flexible key-value storage. Implement hashing for URL shortening and handle collisions. ## Complexity Consider the impacts of traffic patterns on database design and performance. **Time:** Varies based on design. **Space:** Ensure efficient use of database space for stored URLs. ## Trade-offs - Discussion of consistency vs. availability in scaling.