Design a URL shortening service like Bit.ly. The system should take a long URL and return a shorter, unique URL that redirects to the long URL when accessed. The system should be able to handle high read and write traffic. Describe the architecture, including the database schema and key components in your design. How would you ensure that the service scales effectively? Consider aspects like how you will generate unique keys and how storage is handled.

To design a URL shortening service, we would start with a load balancer in front of multiple application servers to handle traffic. Each application server handles incoming requests, generates a unique ID (like a base62 encoding), and stores the mapping to the long URL in a database (like PostgreSQL or NoSQL). The database schema could consist of a table with `id`, `long_url`, and `created_at` fields. To scale, we might implement caching (using Redis) for high-read patterns, and we would use a distributed database for redundancy. The unique ID generation could use a combination of incremental counters and hashing to ensure uniqueness.