Roman Stetsenko, Developer in Kharkiv, Ukraine
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Roman Stetsenko

Verified Expert  in Engineering

iOS Developer

Kharkiv, Ukraine
Toptal Member Since
October 22, 2012

Roman is a skilled mobile developer with expertise in iOS, iPadOS, watchOS, and tvOS. He has an excellent feel for developing apps with a beautiful UI and a high-level UX. His logical thinking, mathematical background, orientation in programming patterns, and ready-to-use third-party solutions are invaluable for creating complex applications. Roman is always attentive to detail and focused on delivering code in time and according to specifications.


WatchOS, tvOS, iOS, Objective-C, Swift, Internet of Things (IoT), SQL, Figma...
Duolingo, Inc.
iOS, Swift
Objective-C, SQL, Core Location




Preferred Environment

MacBook, Git, Xcode

The most amazing...

...thing I've built is an app for teachers called Plickers, where students make responses, and the app provides immediate results to the teacher.

Work Experience

iOS Developer

2013 - PRESENT
  • Created modern apps from scratch according to provided design.
  • Examined existing code and made improvements quickly and without breaking anything.
  • Managed GPS, Bluetooth, Accelerometer, and other device sensors.
  • Worked with various video, photo, and audio generation and manipulation with AVFoundation, GPUImage, AudioKit, and other tools.
  • Deployed various services to apps, such as AWS S3 uploads, Mixpanel analytics, Stripe payments, Mapbox custom maps, Firebase Auth, Realm database, and many more.
Technologies: WatchOS, tvOS, iOS, Objective-C, Swift, Internet of Things (IoT), SQL, Figma, Core Bluetooth, Amazon Web Services (AWS), Core Location

iOS Developer

2022 - 2022
Duolingo, Inc.
  • Helped to launch MVP off the ground by squashing bugs and implementing small features.
  • Planned my work ahead, to avoid gaps due to time difference.
  • Implemented data-based multi-chained intro animation with Core Animation.
Technologies: iOS, Swift

iOS Team Leader

2013 - 2013
  • Handled video and audio recording and playing in the app.
  • Implemented social media integration (Facebook and Twitter).
  • Handled app analytics (Flurry, GA, New Relic, and more).
  • Provided continuous integration (Jenkins and Xcode bots).
  • Improved team-management skills and gained more understanding of people motivation.
Technologies: Objective-C, SQL, Core Location

iOS Developer

2012 - 2013
  • Created an iOS app with an asynchronous video downloader.
  • Created an Instagram-like application with a simple photo editor.
  • Worked with data caching and updating. Optimized network requests for low-speed networks.
  • Worked with Grand Central Dispatch and multithreading.
  • Created an audio preview with the AVFoundation framework.
Technologies: Objective-C, SQL, Core Location

iOS Team Leader

2011 - 2012
  • Managed the team of two iOS developers who worked on different projects.
  • Communicated with the client to create a development plan.
  • Used 3D augmented reality to show location pins with the description on the camera view.
  • Worked with maps, GPS, and compass to show direction hints. Used the MapKit, Core Motion, and Core Location frameworks.
  • Worked with Core Animation to implement custom animations.
Technologies: Objective-C, SQL


The best rated TV App in Switzerland with more than 150 TV channels. I worked on the iOS and tvOS apps.

Key points:
- In the iOS app, I added a recording feature and made small improvements to existing Objective-C code.
- The tvOS app was rewritten from scratch using Swift with a reactive paradigm (RxSwift and RxCocoa).
- In-app purchases and subscriptions were implemented.

Plickers is an app for teachers that allows them to poll the class without the need for student devices. Just give each student a card (a "paper clicker"), and use your app to scan them to do instant checks for understanding, exit tickets, and impromptu polls.

I developed the redesign for the existing iOS app.

Key points:
- Optimized for iPhone and iPads.
- Card scanning feature based on OpenCV.
- Business logic that replicates existing Kotlin code in Android project.
- Refactored from pure Objective-C to pure Swift code with small steps and without interrupting release schedule.
- Offline usage with synchronization when the connection is restored. Used Realm database.


The CareTraxx Platform is a user engagement solution for populations of patients and caregivers.

Its intuitive, mobile-first design improves the cost, quality, and experience of care.

Key points:
- Maintained a high level of security for the app to meet health industry standards
- Tested against common software security weaknesses
Indoor and outdoor navigation
- List of features and UI style can be customized for hospitals.
- Mixed Swift and Objective-C project

GetPerfect allows you to manage your food safety work as effective as possible, makes it effortless to complete routine checks, tasks, and more. I have developed the initial version of the iOS app.

Key points:
- Optimized for iPhone and iPod Touch.
- Can work offline with synchronization when the connection is restored.
- Can be customized per company with brand colors and images
- Written in Objective-C

Happy Studio

Official application for the Happy Studio website by McDonalds. I developed the initial version of this app for iOS.

Key points:
- Optimized for iPhone and iPad
- Mini games written with Cocos2D framework
- QR code recognition
- Developed with strict deadlines because the marketing campaign and printed production were already scheduled
- Written in Objective-C

iOS native app for Cryptocurrency exchange platform

I have been working on iOS app for platform that offers cryptocurrency exchange and other DeFi services.
There are was two iOS developers. I played non lead role in this project and the app is written in SwiftUI
2003 - 2009

Spetialist Degree in Automation and Instrumentation

National Technical University «Kharkiv Polytechnic Institute» - Kharkiv, Ukraine


Google Maps, libdispatch, RxSwift, RxCocoa, GPUImage, Firebase iOS SDK, Shopify API


Xcode, Interface Builder, Git, Figma, PaintCode, Sketch, Adobe Photoshop, Zeplin, Apple HomeKit


iOS SDK, UIKit, Core Location, MapKit, PushKit, Core Bluetooth, SwiftUI, Combine, Cocos2d


Mobile Development, Agile Software Development, Concurrent Programming, Model View Controller (MVC), Design Patterns, Object-oriented Programming (OOP), Model View ViewModel (MVVM)


Swift, Objective-C, Kotlin, Swift 5, Swift 4, GraphQL, SQL, JavaScript, Ruby, Bash, HTML, CSS, HTML5


tvOS, WatchOS, iOS, Amazon Web Services (AWS), AWS IoT Core, MacOS, Firebase

Industry Expertise



SQLite, Realm, MySQL, MongoDB, Amazon DynamoDB


Mobile App Development, AVFoundation, Near-field Communication (NFC), Early-stage Startups, UI Animation, Social Networks, Internet of Things (IoT), MacBook, iPadOS, Kotlin Multiplatform, Arduino IDE, Cryptocurrency, CI/CD Pipelines, Messaging, eCommerce

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