Capsula

Inspiration

When I was 16, I made a little paper airplane and wrote down on it the things I wanted to achieve by the end of the year. It was 2016, and I wrote things like dancing better, learning a new language, meeting girls, and completing a college project. I hid it among my books, and I hid it so well that I didn’t see it again until 2022. At that moment, reading my own words filled me with tenderness, and I loved the feeling so much that I hid it again deep inside the book I was least likely to open for a long time. This year, I found it again in the middle of a house move, and rereading it felt like a trip back in time. Ten years ago—a drastically different life and a teenage version of myself who reminded me of details that have shaped who I am today. That reminded me of how much I wanted a backyard to bury memory capsules in. That’s why I decided to create Capsula—as that digital backyard. A place to treasure memories and tie them to a specific moment: a decade, a birth, a wedding, a graduation. Whatever you can imagine—even the most ordinary things happening to you right now—is a potentially awesome trip back in time.

What it does

Capsula seals photos, videos, notes, sounds, or any digital file inside an encrypted capsule that can only be opened on a designated date. We use a dual custody system: we only store keys on our server, while your phone holds both the encrypted capsule and a QR code to unlock it; this way, we never see your files and can monetize the service without subscriptions. Your capsule is yours forever.

How we built it

Cursor + Flutter + Hono = impressive speed. The front end is built with Flutter, which maximizes speed by being cross-platform with a single codebase. It’s hosted on GitHub, using Actions and Codemagic in a small CI/CD pipeline to maximize deployment speed while maintaining quality. The backend is built with TypeScript using Hono as the framework. It’s hosted on GitHub and also deployed with Actions to Cloud Run. User data, as well as encrypted key envelopes, are stored in Supabase. All of this is powered by a $20-per-month budget for Cursor, during which I stop coding to thoroughly review every change made by the agents, guiding the architecture and the product.

Challenges We Faced

The biggest challenge was answering the key question: How can we ensure that users trust their data will remain secure even after decades on our servers? The answer is: by letting them safeguard it themselves. That’s how the idea of shared custody gained strength.

Accomplishments We’re Proud Of

The entire project was set up in less than a month, with a solid, tested, and scalable architecture.

What we learned

The most important thing we’ve learned from Shippaton is that simply building the app isn’t enough these days. Effective distribution is essential.

What’s Next for Capsula

The long-term goal is to bring the capsules into the physical world. We want the digital key to become a physical object that, in turn, holds the encrypted digital archive. This way, we can offer a complete experience where one or more people can enjoy a capsule that transcends a mere digital space.

Built With

• amplitude
• astro
• bun
• cloudrun
• codemagic
• cursor
• firebase
• flutter
• gcp
• github-jobs
• google-cloud
• hono
• kms
• postgresql
• revenuecat
• supabase
• typescript
• zod