Part 3: Building a Complete URL Shortener

In Part 1, we saw the problem: vibe coding collapses under its own weight.

In Part 2, we introduced the methodology: Functional Block Design — Decomposition, Block Specs, Generation, Integration.

Now we put it all together.

This part contains the complete, runnable URL shortener built with FBD. Every block is here. Every .py file is complete. You can copy these files, run them, and see a working system.

By the end of this post, you will have everything you need to try FBD on your own project.

3.1 The Complete File Structure

Here is every file in the project:

text

project/

├── url_validator.py # Complete

├── key_generator.py # Complete

├── storage_manager.py # Complete

├── redirect_handler.py # Complete

├── analytics_recorder.py # Complete

├── api_router.py # Complete

└── main.py # Integration - Run this

Every block follows the same pattern:

Header with Description (for humans) and Prompt (for AI)

Generated code below the header

One public function…