ReminderOS

Inspiration

I’ve always enjoyed productivity apps, so building a reminders app felt like a natural fit. When Sam Beckman introduced the idea, it immediately resonated with me because reminders sit at the centre of people’s daily lives - they help you stay organised and focused on what matters. I was inspired by the idea of giving users more control over how reminders work, from precise timing to flexible repeat schedules and turning something simple into a really polished, impactful product.

What I Learned

The biggest learning experience for me was working with CloudKit. I’d never used Apple’s native sync infrastructure before, so learning how to store, fetch, and sync reminders across devices was hugely valuable. It taught me a lot about distributed data, conflict resolution, and how to keep datasets consistent across multiple devices while maintaining performance and reliability.

How I Built the Project

I built the entire app using the Codex Desktop App with Codex 5.3 and Cursor. It allowed me to move quickly scaffolding features, iterating on UI, and refining logic in a fast, conversational workflow. The app itself is fully native iOS, using Swift, CloudKit for syncing and Apple’s UserNotifications framework to deliver reminders.

Challenges

The main challenge was ensuring reminders synced across devices quickly and reliably. A reminders app depends on trust - if something doesn’t sync, the experience breaks. I had to carefully handle CloudKit subscriptions, background updates, and data consistency to make sure reminders appeared and updated in near real time while still feeling seamless to the user.

Built With

• cloudkit
• ngrok
• postgresql
• railway
• typescript
• uikit