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Marcin Kmiec, Software Developer in Kraków, Poland
Marcin Kmiec

Software Developer in Kraków, Poland

Member since March 18, 2015
Marcin is a mobile software developer with ten years of professional programming experience. He has completed numerous successful iOS and Android projects working for a big multinational as well as for small and medium businesses. Marcin is able to deliver top-notch quality code as well as prioritize results over anything else. For the past year he has worked on building mobile versions of Unity applications both for iOS and Android.
Marcin is now available for hire



  • iOS SDK, 6 years
  • REST, 6 years
  • Objective-C, 6 years
  • C#, 5 years
  • Core Data, 3 years
  • Android, 3 years
  • Swift, 3 years
  • Unity, 2 years
Kraków, Poland



Preferred Environment

Xcode, GitHub, Bitbucket, Trello, Pivotal Tracker

The most amazing...

...thing I've developed is emotion detection software covered by Techcrunch.


  • iOS and Machine Learning Engineer | Mobile Game Development

    2015 - 2019
    • Led a team of five developers working on an AI-powered social app.
    • Trained custom deep neural network classifiers (work covered by Techcrunch).
    • Created mobile versions of Unity applications (games and AR apps).
    Technologies: Swift, Objective-C, Keras, Unity
  • Objective-C Developer

    2015 - 2015
    Michael Osofsky (via Toptal)
    • Developed a dating app from scratch.
    • Implemented pixel-perfect graphic design.
    • Worked closely with a distributed team.
    • Performed API tests and assisted during back-end development.
    • Handled submission to the App Store.
    Technologies: Objective-C
  • Objective-C Developer

    2015 - 2015
    BookSwapper (via Toptal)
    • Developed an iOS app from scratch in Objective-C.
    • Developed a scalable Parse back end with custom cloud code.
    • Integrated in-house ads using MoPub.
    • Implemented scalable server-side search.
    • Handled the App Store submission process.
    Technologies: Objective-C, Parse, JavaScript
  • Swift Developer

    2015 - 2015
    Spooky, Inc. (via Toptal)
    • Developed an iOS app using Alamofire networking framework.
    Technologies: Swift
  • iOS Developer

    2014 - 2015
    • Developed new as well as analyzed and improved existing iOS applications in Objective-C using a number of frameworks and technologies including Core Data, multithreading (GCD, NSOperation), and multiple communication stacks.
    • Created an augmented reality app for a car manufacturer using Metaio framework.
    • Ported a BlackBerry app into iOS with full data encryption.
    • Worked on a quiz application that used websockets to maintain the connection with the web service in real time.
    • Used unit and functional tests in a continuous integration environment.
    Technologies: Objective-C
  • iOS Developer

    2013 - 2015
    • Developed a location tracking app with continuous background location updates and balanced battery usage.
    • Coordinated web service development with an external developer.
    • Wrote an iOS client of a popular social news website that's nearly topping the US App Store chart in its highly competitive category.
    Technologies: Objective-C
  • Computer Vision Researcher

    2011 - 2014
    AGH University of Science and Technology
    • Performed research on object detection in images.
    • Implemented various computer vision algorithms in C/C++ using OpenCV.
    • Designed software architecture of a real-time computerized CCTV system.
    • Created an in-house image database accesible through a RESTful API.
    • Performed code reviews.
    Technologies: C++, OpenCV
  • PhD Student Contractor

    2009 - 2012
    ABB Corporate Research Center Krakow
    • Developed embedded software for power-grid control devices.
    • Designed, developed and maintained user-friendly C/C++ software libraries.
    • Integrated third-party middleware.
    • Developed reference designs.
    • Supervised junior developers.
    Technologies: C/C++


  • Polygram (Development)

    Polygram was a social app that detected facial reactions to shared photos and videos.

  • Portal App (Development)

    Augmented Reality application running on iOS and Android developed in Unity3d.

  • Liveclip iOS (Development)

    Live Photo editing app for iOS.

  • Liveclip Android (Development)
  • Book Swapper (Development)

    App aimed at college students allowing them to buy and sell their textbooks. Developed both the iOS app and Parse back end with JavaScript cloud code.

  • Hacker News Client (Development)

    First Hacker News client on the AppStore using the official Firebase API. Very successful app with a lot of reviews and a five-star rating in the US.

  • CoffeeOrBeer App (Development)

    Location-based app using Square API and Google Maps SDK.

  • Augmented-Reality iPad App (Development)

    iPad app using Metaio augmented-reality framework used to train car dealers in Germany.

  • DriverRadar (Development)

    An iOS location tracking app with continuous background location updates and balanced battery usage developed for a restaurant in Ireland to optimize their food delivery process.

  • iOS Secure Data Storage App (Development)

    Application aimed at corporate users to securely store classified information.

  • Scientific Journals Search Engine for Poland's Scientists (Development)

    I developed this site back in 2012 to solve my own problem of searching through a PDF list of some 20 000 scientific journals, which took forever. I scrobbled the list into a MySQL table and implemented a search as you type with JavaScript and PHP. The website went viral and now enjoys around a thousand visits a day.

  • Tutorial on Using RESTKit Framework with Core Data (Other amazing things)

    This blog post of mine aimed at intermediate iOS developers has made it to the first page of Google results for "RESTKit tutorial," enjoys roughly a hundred visit a day, and has been recommended by numerous developers.

  • Simplifying RESTful API Use and Data Persistence on iOS with Mantle and Realm (Publication)
    A large number of modern mobile applications interact with web services in one way or another, and iOS applications are no different. Mantle (a model framework) and Realm (a mobile database) come with the promise of simplifying some of the hurdles in consuming web services through RESTful APIs and persisting data locally. In this article, Toptal engineer Marcin Kmiec shows how to build a simple iOS application using Mantle and Realm and demonstrates how this approach helps to eliminate a large amount of boilerplate code.


  • Languages

    Swift 4, C, C++, Objective-C, Java, Kotlin, Swift, C#, PHP, JavaScript
  • Frameworks

    Core Location, iOS SDK, AFNetworking, Unity, Swagger, Core Data
  • Libraries/APIs

    Parse SDK, OpenCV, Alamofire, Socket.IO
  • Tools

    Git, Xcode
  • Paradigms

  • Platforms

    Firebase, iOS, Android
  • Other

    User Interface (UI), Front-end, SAP SD, WebSockets
  • Storage

    Realm, MySQL


  • PhD in Computer Vision
    2009 - 2013
    AGH University of Science and Technology - Krakow, Poland
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