System requirements

URL Shortening: The service should take a long URL and return a shortened URL.
Redirecting: When a shortened URL is visited, it should redirect to the original long URL.
Custom URLs: Users should be able to create custom shortened URLs.
Analytics: Track metrics such as the number of clicks for each shortened URL.
User Accounts: Allow users to create accounts to manage their shortened URLs.
Expiration: Users may choose to set an expiration date for their shortened URLs.
Batch Shortening: Allow users to shorten multiple URLs in one request.

Scalability: The system should be able to handle a large number of requests and scale horizontally.
Performance: The URL shortening and redirection process should happen in milliseconds.
Reliability: The service should provide a high availability to minimize downtime.
Security: Ensure the system protects against malicious URLs and attacks.
Usability: The user interface should be simple and intuitive.
Data Persistence: Store the mapping between shortened URLs and original URLs reliably.