Architecture

A URL shortener seems harmless – but if implemented incorrectly, it opens the door to phishing, enumeration, and data leakage. In this first part, I’ll explore the theoretical and security-relevant fundamentals of a URL shortener in Java – without any frameworks, but with a focus on entropy, collision tolerance, rate limiting, validity logic, and digital responsibility. The second part covers the complete implementation: modular, transparent, and as secure as possible.