Senior iOS Engineer · Warsaw, PL

Ten years of iOS.
Fifty-plus apps.

I'm Dzionis — a senior iOS engineer in Warsaw. Over 10+ years I've designed and shipped 50+ App Store apps, from simple REST clients to geolocation and AR. I've led iOS teams, mentored juniors, and these days I also build and ship my own products.

iOS experience
10+ yrs
In software
15+ yrs
Shipped
50+ apps
Based
Warsaw, PL
Fintech
StoreKit 2 · live rates · in-app purchases
Health & Fitness
HealthKit · WorkoutKit · Core Motion
IoT
Core Bluetooth · iBeacon · Core Location
Entertainment
AVFoundation · audio · playback
Photo & Video
AVCapture · Vision · Core Image
AR
ARKit · RealityKit · SceneKit
scroll
Work

What I'm building, and what I've shipped.

End-to-end iOS — from the first Xcode project to the App Store listing. Here's what I'm working on now, plus highlights from a decade of releases.

Now — building solo

iRunning

Beta · TestFlight

Interval running for Apple Watch. Build a workout, run it from your wrist, and review the route afterward. Watch-first, with no subscription wall.

SwiftSwiftUIWorkoutKitHealthKitWatchConnectivityMapKit
  • GPS route smoothing with a Kalman filter and Douglas–Peucker simplification, so wrist traces stay clean.
  • Real-time heart rate streamed from the watch to the phone during a live session.
  • One-tap Strava export over OAuth 2.0.

Currency Converter: Live Rates

Live · App Store

Fast conversion across 160+ world currencies with daily-updated rates — a small, focused travel companion that doubled as a real growth experiment.

SwiftSwiftUIasync/awaitStoreKit
  • Scan any price tag with the camera, set a base currency, and pin your favourites.
  • Full ASO program: 200+ Apple Search Ads keywords and icon A/B tests via custom product pages.
View on App Store

Voice Memos: AI Audio Recorder

Live · App Store

A clean, high-quality voice recorder with playback and in-app trimming — plus one-tap transcription that turns what you said into text.

SwiftAVFoundationSpeechStoreKit
  • Waveform recording with playback and precise trimming.
  • Speech-to-text transcription, with export and sharing.
View on App Store

Text to Speech: AI Book Reader

Live · App Store

Turns any text, document or photo into natural-sounding speech — listen instead of read, whether you're studying, working or on the move.

SwiftAVFoundationVisionPDFKitStoreKit
  • 140+ natural voices across 38 languages, with tunable speed and pitch.
  • Imports from PDF, documents and photos (OCR); highlights spoken text with auto-scroll, and works offline.
View on App Store

Highlights from 50+ shipped App Store apps

System Technologies · 2018–2022 · fintech & transport for Belarusian clients
Drive&Pay
Pay for fuel at the pump straight from your car, across the Belarusneft station network.
Tix
Contactless fare payment and e-tickets for city public transport.
Дзякуй
Cardless fuel payment at A-100 stations — pay from the car without leaving the pump.
Звезда
Loyalty and rewards app — collect and redeem points with a card linked in-app.
  • Full-stack when needed: I built PartyCam's backend in Python on Firebase (Firestore + Cloud Functions), plus PHP chat backends on other projects.
Experience

A decade-plus, shipping iOS.

From web and backend beginnings to leading an iOS team and going independent — releasing apps the whole way.

2026 — Present

Independent iOS Developer

Self-employed (JDG) · Warsaw

Building and shipping my own products — iRunning chief among them — and running the growth side myself, from App Store optimization to release strategy.

SwiftSwiftUIwatchOSASO
Jan 2022 — Apr 2026

iOS Developer

ASAP Visuals, Inc. · Warsaw

Developed and supported five App Store apps (izi AI, izi Type, PartyCam, Edith, Templates) across internal and outsourced projects, with ongoing updates and refactoring — and built backend services too: PHP for chat, Python on Firebase for PartyCam.

SwiftUIKitPHPPythonFirebase
Aug 2018 — Jul 2022

Lead iOS Developer

System Technologies · Minsk

Led the iOS team — architecture, project management, mentoring junior developers, and working directly with foreign clients. Shipped 5+ App Store apps (Drive&Pay, Tix, Дзякуй, Звезда and others) and helped run the company's internal education program of weekly talks and workshops.

iOS LeadArchitectureMentoringApp Store
Jun 2017 — Jun 2018

iOS Software Developer

EffectiveSoft Corporation · Belarus

Built and released three App Store apps on long-term client projects, with regular updates and refactoring.

Nov 2015 — Apr 2017

iOS Software Developer

Goozix

Shipped 10+ App Store apps, owned architecture on iOS projects, mentored juniors, and contributed to internal education — workshops and news digests.

Feb 2014 — Nov 2014

iOS Developer

Wellnuts Creative Group · Minsk

Prototyped and shipped 5+ iOS apps for the agency and its clients.

2011 — 2014

Web & Backend Developer

Maksis · Qulix Systems

Where it started: Yii-based CMS, Yandex widgets, social-promotion tools, and backends for mobile apps.

Skills

The full toolkit.

A decade of iOS, from language internals to monetization and CI/CD — the stack I reach for, end to end.

Languages
Swift (incl. Swift 6), Objective-C
UI
UIKit, SwiftUI, WidgetKit (widgets, Live Activities), watchOS (WatchKit / SwiftUI), Auto Layout, Core Animation
Architecture
MVVM, Redux / Unidirectional Data Flow, Clean Architecture, modular design (SPM)
Concurrency & Reactive
Swift Concurrency (async/await, actors), GCD
Graphics & Media
Core Image (custom filter kernels), AVFoundation / AVCapture, Camera Control API, Vision, Core ML, color management
Monetization
StoreKit 2, RevenueCat, Adapty, Apphud, paywall & pricing A/B testing, subscription analytics (LTV, retention, conversion)
Analytics & Attribution
Firebase (Analytics, Crashlytics, Remote Config), Amplitude, AppsFlyer, Adjust, Facebook
Data & Networking
Core Data, SwiftData, Realm, Keychain, URLSession, REST, Codable
Hardware & IoT
Core Bluetooth (BLE), iBeacon, Core Location, HealthKit
Design Collaboration
Figma, Zeplin, Sketch, design-to-code workflow, attention to UI detail & UX
Testing
XCTest, Unit / UI testing
CI/CD & Tooling
Fastlane, Xcode Cloud, Git, SPM, CocoaPods, App Store Connect, TestFlight, Instruments
Writing

Notes from the build.

Short, practical write-ups on the things I hit while shipping. First full posts are going up now — more on the way.

All writing
About

I'm a senior iOS engineer based near Warsaw, with 10+ years building for the platform and 15+ years in software overall. I've shipped 50+ apps to the App Store — from straightforward REST clients to geolocation and AR — for startups and mid-size companies.

Along the way I led an iOS team, owned architecture, mentored junior developers, and worked directly with international clients. When a product needed it, I went full-stack — building backends in PHP and Python on Firebase.

These days I build and ship my own products, like iRunning, and stay close to the parts beyond the code — App Store optimization, growth, and the craft of a release people actually keep. I work across English, Polish and Russian.

Contact

Have an iOS idea, or hiring?

Senior iOS engineer, open to strong product work, contracts and collaborations. Quickest ways to reach me: