Currency Converter

Inspiration

As a frequent traveler across Europe and beyond, I grew frustrated with clunky, unreliable currency converters—either slow, offline-unfriendly, or lacking precision. I wanted a tool that felt seamless, visually polished, and built for the real-world chaos of travel: spotty internet, quick calculations, and easy access to favorite currencies. That’s how MEDO was born.

What it does

MEDO is a travel-focused currency converter that delivers real-time, precise conversions for 150+ global currencies. It works offline (using 24-hour cached rates), stores favorite currencies (up to 10), tracks conversion history (100 records), and includes an admin panel for API management, logs, and version control—all wrapped in a modern, intuitive UI.

How we built it

We started with core conversion logic (following international standards: $1\text{ CNY} = x\text{ JPY}$, 0 decimals for JPY, 4 for others) and built a responsive React frontend aligned with a strict design system. We integrated dual exchange rate APIs with auto-failover, implemented LocalStorage for offline caching, and added smooth animations (swap button rotation, result fade/slide) for a premium feel. The admin panel uses Node.js/Express for backend logic, with encrypted API keys and Excel export for logs.

Challenges we ran into

The biggest hurdle was balancing real-time accuracy with offline functionality—ensuring cached rates were clearly marked as stale (>24h) while still allowing conversions. We also struggled with consistent animation performance across mobile/desktop, and API rate limits forced us to optimize call frequency (1-hour auto-refresh) and build robust failover logic.

Accomplishments that we're proud of

We nailed the 0.0001 conversion accuracy target, built a UI that’s both beautiful and functional (consistent color palettes, spacing, motion), and created an admin panel that’s secure (encrypted credentials) and user-friendly. Most importantly, MEDO works flawlessly offline—something many competitors overlook.

What we learned

We deepened our understanding of API reliability and failover design, mastered responsive animation best practices, and learned to prioritize user trust (clear offline warnings, transparent rate updates). We also realized how critical local storage optimization is for mobile-first tools.

What's next for this project

While v1 focuses on core functionality, we’re exploring adding rate trend alerts (for frequent travelers), expanding currency metadata (local usage notes), and refining the admin panel with real-time API analytics. We also want to optimize load times further for low-bandwidth regions—making MEDO even more travel-ready.

Built With

• chart.js
• exceljs
• open-exchange-rates