Inspiration
It all started when my sister complained to me about currency notes, exchange rates, and stuff after her trip to Bali; she was annoyed that every transaction was in cash. Coming from India, we use UPI (Unified Payment Interface) extensively here for transactions. That's what inspired me to build this cross-border payment app, similar to India's UPI but specifically for international transactions.
What it does
GlobalPay brings together currency insights, merchant payments and AI-powered assistance in one platform. Travellers can explore indicative exchange rates, understand currency conversions, discover local merchants and make payments in the merchant's local currency through PayPal Sandbox.
We also integrated a Gemini-powered travel payment assistant to provide contextual guidance and help users navigate payment-related questions.
How we built it
We built GlobalPay as a mobile-first Progressive Web Application using Next.js, React, TypeScript, and Tailwind CSS, with a MySQL database managed through Prisma. PayPal Sandbox powers the payment flow, while Gemini provides the AI assistant experience. Frankfurter supplies indicative foreign-exchange reference rates.
We focused on building a secure backend foundation, incorporating session ownership checks, request validation, payment idempotency and server-side payment verification.
Challenges we ran into
One of our biggest challenges was implementing a reliable cross-border payment lifecycle. Integrating PayPal Sandbox involved handling merchant and buyer account configurations, currency compatibility, payment approval, capture verification and uncertain payment states.
We also encountered intermittent AI API availability issues and had to improve model configuration and error handling to make the Gemini assistant more reliable.
Balancing a polished, intuitive frontend with robust backend security and payment integrity was another significant learning experience.
What we learned
Building GlobalPay taught us that a payment experience is much more than a checkout screen. Currency accuracy, transaction integrity, security, error recovery, and user trust all matter.
We gained practical experience integrating third-party APIs, designing payment workflows, building AI-powered features, and applying security principles to a full-stack application.
GlobalPay is our exploration of a simpler, more connected way to experience payments while travelling internationally.
What's next for GlobalPay
Right now, the app only considers tourists who are physically travelling. I want to extend the scope of the project so that it works when I sit at at home and make an international payment. And I want to add more countries to the list as well.
