From altitude sickness to the app store with Expo Router, ElysiaJS, and Nativewind

Last summer I failed.

I set out to conquer my first 5,000m mountain. But at 4,000m, waiting for sunrise, altitude sickness hit me hard. I had to turn back. My group summited, I didn’t.

That failure stuck with me. So I started climbing more. Getting stronger. And as a software developer I decided to over-engineer a solution to track my summits.

That’s how 100cims was born: a personal app that became a passion project.

100cims is a mobile app for mountain lovers. It lets users:

• Track mountain summits across challenges ( 🇺🇸 US top 150 mountains, 🇪🇸 Catalonia’s 100 cims, 🇫🇷 GR-20 Corsica, 🇪🇺 European Alps…).
• Earn scores based on mountain difficulty and elevation.
• See summit history with a visual collage of photos.
• View a public ranking and compare with friends.
• Create and join hiking plans with built-in chat 💬.

In under 4 months, 100cims has grown to over 200+ users with 1,000+ summits logged — all 100% organic.

• 🤖 On Android.
• 🍏 On iOS.
• ⭐ On GitHub.

The app is built entirely in React Native, powered by Expo.

On the app:

• expo-router powers navigation — bringing file-based routing to React Native with nested layouts, dynamic routes, and modals that just work.
• nativewind lets me use Tailwind-style utilities directly in React Native. It makes styling fast, scalable, and developer-friendly.
• A suite of Expo SDKs powers native interactions: expo-store-review, expo-image-picker, expo-haptics, expo-clipboard, expo-device, and more.

The experience across platforms (iOS and Android) is seamless — and thanks to expo-dev-client, development is smooth and blazing fast.

Under the hood, the backend runs a typed, minimal setup using Elysia.js, a modern Bun framework that feels like Fastify meets tRPC. It’s built around composability, types, and performance.

• API routes are organized into public and protected groups
• Auth is handled with a JWT + Bearer strategy, using @elysiajs/jwt and @elysiajs/bearer
• Database access is powered by Drizzle ORM, giving me schema-safe queries with type inference on a PostgreSQL DB hosted on Supabase.
• All API routes are mounted via expo-router, similar to next.js api routes.

To fetch data on the client, I use React Query (@tanstack/react-query) together with Eden, an Elysia companion from which I get full end-to-end type safety between the API and the app — no manual types or duplication. One repo, fully typed, from database to UI.

100cims continues to grow — the new "Plans" feature (with internal chat per group) is already helping hikers organize their adventures together. And the next update will bring a fully interactive map view for discovering mountains near you.

Future updates will focus on:

• Gamification features (badges, titles, awards).
• Challenge creation by the community.

If you love hiking, climbing, or just want to follow the journey:

• 🤖 On Android.
• 🍏 On iOS.

Explore the solution:

• ⭐ On GitHub.

This app started as a way to fix a personal failure. But now it’s something that others use, love, and build real memories with. If you’ve ever wanted to build something from scratch with Expo — you can.

This summer I'll reach the summit. And I hope some of you will get there with me.