After a few months of building in my spare time, I shipped r/CartLens and launched on Product Hunt and PeerPush. The idea was simple: snap a receipt or archive a shopping trip, and the app tells you if you overpaid compared to real prices at other stores nearby.
The hard parts nobody talks about:
- Thermal paper fades. Getting AI to read a crumpled, half-faded receipt reliably took way longer than I expected
- Normalizing product names across stores is a nightmare ("Organic Whole Milk 1L" vs "Whole Milk Organic 1000ml" are the same thing — teaching a model that at scale is non-trivial)
- Building a crowdsourced price index from scratch means your product is useless until you have data, but you can't get data until people use it — classic cold start problem
Happy to answer questions about the stack or any of the above. Built with React, Gemini 2.5, Supabase, and more pain than I anticipated. cartlens.co
u/AdEfficient8374 — 6 days ago