Konstantin M.

I build complete mobile products: Android and iOS apps, the backends behind them, and companion experiences for macOS, desktop and web. My work spans product interfaces, application architecture, APIs, data and release delivery. I'm a senior developer based in Sydney, with 5+ years in mobile development. Top Rated Plus on Upwork, with $40K+ earned. I work with founders building a new product and teams improving an existing one. I can take responsibility for a complete feature across the app and backend, or join your team to deliver a specific part. WHAT I CAN HELP YOU BUILD • Android and iOS apps — from the first core user flow through implementation, integrations, store release and ongoing development. • Apps across platforms — shared Kotlin Multiplatform and Compose Multiplatform implementations, macOS and desktop experiences, and Swift/SwiftUI or other native platform work where it fits the product. • Backends and APIs — custom services with Ktor, PostgreSQL and Exposed; data modelling, authentication, Firebase features and integrations with external systems. • Features for existing products — payments, offline data, notifications, media playback and API integrations, alongside architecture, performance and reliability improvements. SELECTED WORK • Suby — my independently built subscription tracker, released on Android and iOS, with 5K+ downloads on Google Play. I work across the product, interface, implementation and ongoing releases. • Maytes / Kttipay — part of a two-engineer team delivering a consumer payments product, with shared Android/iOS features, native payment integrations and Compose UI extended to Paylinks on the web. • FreeDroid — my open-source macOS project using Swift and SwiftUI, with Android-device file browsing, transfers and Finder integration. • Backend and open source — my public projects include FishingBackend, a Kotlin/Ktor server project with PostgreSQL and Exposed. I also co-developed KPayment at Maytes and maintain Kimplify libraries. HOW I WORK We start with the product goal, target platforms and the next useful milestone. I map the app and backend work together, make the shared-code and native boundaries clear, and agree on how we'll verify the result. Core tools: Kotlin, Kotlin Multiplatform, Compose Multiplatform, Jetpack Compose, Swift, SwiftUI, Ktor, PostgreSQL, Exposed, Firebase, Room and Coroutines/Flow. Send me your product idea or existing app, the platforms you need and the next milestone you want to deliver.