URL Shortener Service

Implement a URL Shortener service that supports two main operations: encode and decode.

Requirements:

• The encode function takes a long URL and returns a shortened URL. The shortened URL should be as concise as possible.
• The decode function takes a shortened URL and returns the original long URL.
• Assume the service operates in a multi-user, concurrent environment. Consider strategies to handle potential collisions and ensure scalability.
• You may use in-memory data structures for storage in your implementation, but structure your solution so that it could be extended to more persistent storage.
• Write clean, modular code in a language of your choice. You are free to design and use additional helper functions or classes as necessary.

Provide a complete working prototype demonstrating the encoding and decoding processes.