Inspiration
After losing a previous hackathon, I wanted to challenge myself to come back stronger, learn from my past technical mistakes, and build something genuinely resilient from the ground up. Looking at how online merchants struggle today, I realized small businesses face a similar battle: flat per-transaction fees eat away their margins on low-ticket sales, while sudden API failures or chargeback disputes can wipe out hard-earned revenue. That drive to turn past lessons into a fault-tolerant solution inspired Sentinel Shop Shield—an intelligent layer on top of PayPal that automatically optimizes payment routing by cart value, assists shoppers in real time, and protects merchants against 180-day disputes.
What it does
Sentinel Shop Shield is an AI-powered payment optimization and fraud prevention layer built for PayPal merchants:
- Smart Dual-Route Fee Optimization: Automatically checks every product against a $26.67 USD threshold. Items below $26.67 (like the $15 Wireless Earbuds or $9 USB-C Cable) use the Micro-Fee Route to save up to 4% in fees, while higher-priced items (like the $120 Smartwatch) use the Standard PayPal Route.
- Sentinel AI Shopper Guard: An integrated shopping assistant powered by Google Gemini that recommends products and guides customers through checkout.
- Merchant Auth Guard Dashboard: A real-time control panel that monitors transaction risk, logs evidence for 180-day chargeback protection, and includes a 500 API Error Simulator to test instant payment recovery.
How we built it
We built the storefront and dashboard with React, TypeScript, and Tailwind CSS (prototyped in Lovable), integrated PayPal Sandbox for checkout flows, and combined Google Gemini with a deterministic fallback engine so recommendations and risk checks never stall.
Challenges we ran into
Relying solely on live external AI APIs during checkout can cause delays or 500 errors that block a sale. Building a deterministic fallback layer—and adding a live error toggle in the dashboard to prove zero-downtime recovery—was our main technical challenge.
Accomplishments that we're proud of
- Creating a dynamic PayPal checkout flow that clearly shows fee savings in real time.
- Ensuring transactions still capture smoothly even when upstream AI services simulate an outage.
- Combining a clean storefront and a merchant risk dashboard into one cohesive prototype.
What we learned
We learned how payment fee thresholds affect small-ticket e-commerce margins and why fintech AI tools always need reliable fallback logic so checkout never breaks.
What's next for Sentinel Shop Shield
Next, we want to connect the Auth Guard evidence logs directly to automated PayPal Dispute webhooks, add multi-currency support, and forecast monthly merchant savings.
Built With
- gemini
- lovable
- paypal
- react
- tailwindcss
- typescript
