I built a privacy-first PDF merger in 7 hours — here's the stack and the lessons

TL;DR

Day 8 of building SwapFile.io (privacy-first image/PDF converter) in public. Yesterday I shipped a feature I needed myself: PDF Merge. Total time: ~7 hours from "do we have this?" to production. Stack: Go + Fiber + PostgreSQL + Next.js 16. The interesting bits are about what I didn't have to write.

Live:

The code is closed-source today (might change post-monetization in November). Everything you see in this post is exactly how it runs in production — no oversimplification for the article.

Building .