Shopify App · React · US Market · Client Project

Expert OTO

Custom Post-Purchase Upsell App — Built in 4 Days

"4 days to build. +35% to every order."

+35% Average Order Value Increase
4 Days Build & Ship
Pays Every Day

RationFit sells nutrition recipes on the US market. They were leaving money on the table after every checkout. I built a custom Shopify app from scratch that presents targeted post-purchase offers the moment a customer completes their order. Result: average order value increased by 35% — completely on autopilot.


Post-Purchase Upsell Engine

Built a smart offer engine that triggers immediately after checkout with personalised discount offers — catching customers at peak buying intent when they are most likely to add.

Custom Admin Panel

Engineered a clean admin panel so the RationFit team can independently manage products, names, descriptions and prices in the upsell flow. Zero developer dependency after handoff.

React & Shopify Integration

Built entirely with React and JavaScript, integrated directly with Shopify API. No third-party upsell tools, no monthly fees — complete ownership for the client.

4 Days to Production

Designed, built and delivered a production-ready custom app in 4 days. Full UI matching the store brand, native Shopify checkout feel, ready to ship.


Every order now generates 35% more revenue. A one-time build that pays for itself every day.

+35% average order value Delivered in 4 days Fully autonomous after handoff


React JavaScript Shopify API Custom Admin Panel HTML & CSS