Zsolt Szatmári

Supreme is a daily to-do app for Mac and iOS: tasks live on the day you plan to do them, and unfinished ones roll over automatically. I built the macOS version single-handedly from scratch in Swift and AppKit, along with the core shared between the Mac and iOS apps, and also worked on the UIKit-based iOS version. I implemented offline-first sync with Realm as the local store and CloudKit for the cloud, with no user accounts required. I designed the data model and sync layer to be shared between the Mac and iOS apps.

NewsBar is a Mac RSS reader that shows live news feeds in a bar at the side of the screen or in a regular window, with keyword highlighting and alerts. I took over its development and turned it into a commercial success: it was almost constantly the #1 paid app in the US App Store’s News category. I also built iCloud sync before CloudKit existed, with my own conflict handling, and ported the app to iPhone and iPad.

idunn is an open-source Rust crate for Sign in with Apple on the server: it verifies identity tokens, exchanges authorization codes and revokes refresh tokens. I designed its API to be easy to use correctly and hard to use incorrectly, with many of Apple’s rules enforced by the type system. It caches Apple’s signing keys with single-flight, rate-limited refreshes and keeps credentials out of logs. CI gates every change on mutation testing and 90% line coverage.

RunTogether Runner is the Android app of RunTogether, England Athletics’ community running programme (10K+ downloads). I built most of its features in Kotlin in 2018: an offline-first data layer with an ObjectBox cache that the screens observe, a map-based explore view with location and postcode search and pins synced to a swipeable card list, session booking with Stripe card tokenization, and accessibility filters such as wheelchair access and guide runners.