Yonas Kolb, Developer in Byron Bay, New South Wales, Australia
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Yonas Kolb

Verified Expert  in Engineering

Mobile Developer

Byron Bay, New South Wales, Australia
Toptal Member Since
October 7, 2022

Yonas is an iOS specialist with a keen eye for detail, over 14 years of industry experience, and a passion for building delightful apps. He cares a lot about creating a good developer experience and has a knack for building great developer tools and making systems fast, easy, and fun to work with. His open-source work is used by many of the largest tech companies in the world. Yonas has experience in fintech, video streaming, e-learning, disability, recruitment, games, AI, and productivity.


iOS, Bitrise, Xcode, Code Architecture, User Experience (UX), Greenfield...
Beem It
UIKit, Swift, Xcode, Bitrise, GitHub, Agile, UI Testing, iOS...
Massive Interactive
Swift, Xcode, tvOS, iOS, Video Streaming, HTTP Live Streaming (HLS), Training...




Preferred Environment

iOS, Xcode, Swift, GitHub, Bitrise, Firebase, MacOS, tvOS, SwiftUI

The most amazing...

...app I've built is the Hireup app, which connects people with disabilities with support workers. It has both a great user and developer experience.

Work Experience

iOS Architect and Mobile Engineering Manager

2019 - 2022
  • Architected, developed, and launched a Greenfield iOS app that allowed people with disabilities to find, manage, and hire support workers. Then built a team around it.
  • Worked with stakeholders to define an initial feature set, future roadmap, and basic UX.
  • Created an architecture to work hand in hand with SwiftUI, enabling rapid and easy development. It included one-way data flow, free snapshots, accessibility testing, in-app debug tooling, and system-wide, state-based, and editable component previews.
  • Implemented various developer tools to improve the developer experience, integrated throughout the codebase, app, and CI/CD.
  • Collaborated with platform teams to improve their API contracts, services, and tests, ran an ongoing course to teach Swift and app development in the company, and positively influenced the product team.
  • Built a tight user feedback system to facilitate good communication with users and ensure the problems were being fixed.
  • Developed test infrastructures and tests to ensure confidence in builds.
  • Set up the building pipeline for CI/CD and integrated various services like Firebase, Instabug, Segment analytics, and testing.
  • Launched the app on the App Store with great success and feedback.
  • Interviewed, hired, and managed a team of iOS and Android engineers after the launch of the initial app.
Technologies: iOS, Bitrise, Xcode, Code Architecture, User Experience (UX), Greenfield, SwiftUI, Firebase, Sockets, Instabug, Agile, GitHub, REST, CI/CD Pipelines, App Store, DevOps, Developer Experience (DX), Roadmaps, Management, User Interviews, Interviewing, UIKit, Combine, Push Notifications, Swift, iOS Native Libraries, iOS SDK, Apple, APIs, SDKs, Widgets, UI Animation, Figma, Core Animation, REST APIs

Lead iOS Engineer

2018 - 2019
Beem It
  • Took an MVP app and improved its architecture, tests, performance, and UX.
  • Led a team of four iOS engineers and collaborated with the design, Android, and back-end teams.
  • Improved the app to rank number one on the App Store in Australia.
Technologies: UIKit, Swift, Xcode, Bitrise, GitHub, Agile, UI Testing, iOS, iOS Native Libraries, iOS SDK, App Store, Apple, APIs, SDKs, UI Animation, Core Animation, REST APIs

Lead Mobile Engineer

2013 - 2018
Massive Interactive
  • Architected and built the company's main white-label product Axis, for iOS and tvOS.
  • Spearheaded the mobile team consisting of iOS and Android engineers.
  • Held iOS and Swift training sessions in our offices around the world.
  • Led the building and deployment of several iOS and tvOS apps using Axis.
  • Set up building tools, pipelines, and CI/CD. Worked with the platform and DevOps teams to refine their API contracts and use code generation for client networking.
  • Helped define some of the user experiences for our various apps.
Technologies: Swift, Xcode, tvOS, iOS, Video Streaming, HTTP Live Streaming (HLS), Training, Swagger, Build Pipelines, CI/CD Pipelines, iOS Native Libraries, iOS SDK, Apple, APIs, SDKs, UI Animation, Core Animation, REST APIs

Lead Front-end Developer

2010 - 2013
Wunderkind Group
  • Architected and built Braavio's Flex front end, an online video recruitment platform. Also designed and created the admin portal.
  • Designed the architecture and built the Flex front end and iOS app for Wunderkind Pro, an online e-learning platform.
  • Collaborated with the back-end team in defining API schemas and endpoints.
Technologies: Flex, Eclipse IDE, Flash, AS3, Animation, REST, Video Streaming, Analytics, APIs, SDKs, UI Animation, REST APIs

Flash Developer

2008 - 2010
Massive Interactive
  • Worked on multiple projects, including marketing sites, in-flight entertainment systems, e-learning software, and social media sites. Most of these projects were developed in Flash and Flex as rich internet applications.
  • Built a new employee timesheet tracking app for the company in my spare time.
  • Helped win some jobs with high-quality prototypes.
Technologies: Flex, Flash, AS3, User Interface (UI), User Experience (UX), APIs, SDKs, UI Animation, REST APIs


XcodeGen is an open-source command line tool written in Swift. It helps developers generate Xcode projects on demand from a human-readable specification. This tool removes git conflicts from the project file and lets companies scale up their projects or easily create new white-label projects. It is used by large and small tech companies around the world.

Beem It

A native Swift-based app used to pay and receive money, split bills, and manage cards, acting like a digital wallet. It includes rich interaction patterns and a playful design. As it's a banking app, security was paramount.


A Greenfield SwiftUI-based app I architected, helped design, built, launched, and ultimately built a team around it. It connects people with disabilities with support workers and includes real-time messaging, deep searching, booking and scheduling functionalities, push notifications, sockets, profile and account management, and more. As it functions as a 2-sided marketplace, the app includes bespoke experiences for all types of users, including clients, support workers, and account managers.

The architecture, building system, CI/CD pipeline, tests, and developer tools provided a great user experience and fast iteration time for the team working on this project.

Given the audience, including automated testing of accessibility implementations was a big focus, ensuring great accessibility.


Swift, AS3, Objective-C, Java, Processing, Bash


SwiftUI, Flex, iOS SDK, UIKit, Swagger


iOS Native Libraries, REST APIs, Sockets, Core Animation


Xcode, Instabug, GitHub, Crashlytics, Git, Flash, Eclipse IDE, Figma


iOS, Apple, Bitrise, Firebase, tvOS, Visual Studio Code (VS Code), MacOS, Godot


App Store, Developer Experience (DX), Code Generators, Programming, Command-line Interface (CLI), Software Architecture, Code Architecture, Greenfield, Combine, APIs, SDKs, Graphic Design, Video Production, Architecture, Software Design, Hardware, Industrial Design, Psychology, User Interface (UI), CI/CD Pipelines, Community Growth, Roadmaps, User Interviews, Interviewing, Analytics, Push Notifications, App UX, User Experience (UX), UI Testing, Computer Science, Build Systems, Genetic Algorithms, Physics Simulations, Cryptography, Biometrics, Animation, Accessibility, User Feedback, Video Streaming, HTTP Live Streaming (HLS), Training, Build Pipelines, Image Generation, Widgets, UI Animation, The Composable Architecture (TCA)


Agile Software Development, Agile, REST, Management, DevOps, Test-driven Development (TDD), Testing, Automated Testing

Industry Expertise

Web Design

2004 - 2008

Bachelor's Degree in Design Computing

University of Sydney - Sydney, Australia

Collaboration That Works

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