Koffan

Koffan is a lightweight web application for managing shopping lists, designed for couples and families. It allows real-time synchronization between multiple devices, so everyone knows what to buy and what's already in the cart.

The app works in any browser on both mobile and desktop. Just one password to log in - no complicated registration required.

Why did I build this?

I needed an app that would let me and my wife create a shopping list together and do grocery shopping quickly and efficiently. I tested various solutions, but none of them were simple and fast enough.

I built the first version in Next.js, but it turned out to be very resource-heavy. I have a lot of other things running on my server, so I decided to optimize. I rewrote the app in Go and now it uses only ~2.5 MB RAM instead of hundreds of megabytes!

Features:

• Ultra-lightweight - ~16 MB on disk, ~2.5 MB RAM
• PWA - Install on your phone like a native app
• Offline mode - Add, edit, check/uncheck products without internet (auto-sync when back online)
• Organize products into sections (e.g., Dairy, Vegetables, Cleaning)
• Mark products as purchased
• Mark products as "uncertain" (can't find it in the store)
• Real-time synchronization (WebSocket)
• Responsive interface (mobile-first)
• Multi-language support (PL, EN, DE, ES, FR, PT)
• Simple login system
• Rate limiting protection against brute-force attacks