Jacek Szyja, Software Developer in Swinoujscie, Poland
Jacek Szyja

Software Developer in Swinoujscie, Poland

Member since February 5, 2020
Jacek is an experienced software engineer. During his career, he's had a chance to create projects for small startups and big global corporations. He gained experience in all project phases, from early project discussions and estimations through app development to releasing and analyzing results. Besides app development, Jacek is interested in mobile security.
Jacek is now available for hire


  • Self-employed
    Swift, iOS
  • Goldman Sachs
    iOS, Swift, Xcode, REST, CocoaPods, REST APIs, GraphQL, Charles Proxy...
  • HYD
    Amazon Web Services (AWS), Flow Coordinators, Viper...



Swinoujscie, Poland



Preferred Environment

Git, Xcode, MacOS

The most amazing...

...app I've made was for a fast food chain in UK. The sight of random people using it during my visit to London made me feel proud.


  • iOS Engineer

    2020 - PRESENT
    • Worked with a leading investment bank to help them expand into daily banking.
    • Implemented SAML authentication, allowing US students to borrow ebooks on their phones.
    • Created a social network experience for people working on their mindfulness.
    • Helped people track their personal development progress thanks to beautiful charts.
    Technologies: Swift, iOS
  • iOS Developer

    2021 - 2023
    Goldman Sachs
    • Charged with developing new features and fixing bugs which has the most impact on the end user experience.
    • Implemented Marcus fast track flow which made automatic saving more straightforward and engaging for users.
    • Tasked with adding joint account-related features like showing transaction owner, assigning one if there isn't any, filtering, etc.
    • Uplifted UI on transactions list and transaction details screens.
    • Added many Unit and Snapshot tests throughout the app.
    Technologies: iOS, Swift, Xcode, REST, CocoaPods, REST APIs, GraphQL, Charles Proxy, Postman, Unit Testing, Testing, Figma, Firebase, Git, UIKit, SwiftUI
  • iOS Developer

    2016 - 2020
    • Developed mobile applications for well-established companies and global corporations in industries like food, transportation, photography, bio pharmacy, and more.
    • Performed research projects for an augmented reality app and developed the back end in Swift with the Vapor framework.
    • Developed complex custom UI components and animations.
    • Was consulted about the mobile app and system security.
    • Configured analytics and made usage reports based on gained data.
    Technologies: Amazon Web Services (AWS), Flow Coordinators, Viper, Model View Viewmodel (MVVM), Carthage, Bitrise, ReactiveX, Swift, CI/CD Pipelines, Continuous Integration (CI), Continuous Delivery (CD), Bitbucket, Xcode, RxSwift, Payment APIs, BrainTree
  • iOS Developer

    2015 - 2016
    • Developed internal mobile applications and games for iOS.
    • Developed mobile applications for startups and well-established companies.
    • Worked remotely with clients in different time zones.
    • Estimated the time needed to develop new projects and planned the development schedule.
    Technologies: Model View Viewmodel (MVVM), Carthage, Swift, Objective-C
  • iOS Developer

    2014 - 2015
    • Developed internal mobile application projects targeted at medical students.
    • Redesigned and rewrote the flagship app from scratch.
    • Optimized performance in downloading, manipulating, and saving data concurrently.
    Technologies: Objective-C, Core Data


  • Marcus by Goldman Sachs

    Consumers use this application in the United States and the United Kingdom. This application is the first step of Goldman Sachs to daily banking services. It is written in Swift with most of the UI in SwiftUI and some older components in UIKit.

    I was part of a team responsible for adding new features and fixing bugs. I implemented automatic savings flow, allowing users to save monthly excess cash, features related to joint accounts, UI uplifting of transactions list and transaction details screens, and many smaller features.

  • iOS App for Greggs Fast Food Chain

    The app's purpose was to increase customers' retention by providing them with an incentive program, convenient payment options, and the possibility to browse the menu or locate the nearest store. The app was completely rewritten to use ReMVVM architecture with a RxSwift ReactiveX library. With this release, the client wanted to test a new UI and incentive options on a small trial group, so the app needed to change its entire view depending on a single flag received from the back end. I was the lead developer responsible for rewriting and implementing the new UI. Communication between the client and the back end was secured with OAuth authentication.

  • Library Simplified

    This application is used by public libraries throughout the United States. It allows people to borrow ebooks and audiobooks. It is written mainly in Objective-C, but all new changes are implemented in Swift (some Objective-C chunks are refactored alongside).

    I was responsible for implementing a SAML authentication into the app. This type of authentication is quite popular among universities but isn't widely used in mobile applications. Adding SAML opened the app for many new libraries. Other than that, I refactored some of the OAuth logic, added a new OAuth grant type, and refactored a class responsible for keychain data storage.

  • iOS App for Canon Europe

    The purpose was to educate users on more advanced camera options and introduce users to other equipment produced by the company, including lenses and flashes.
    The app featured content downloaded from the CMS with many different custom presentation types such as exercises, interactive maps, lens comparisons, and more.
    I was a part of a two-person team. Communication between the client and the back end was secured with OAuth authentication.

  • iOS App for Stagecoach UK

    The app was built for the biggest bus company in the UK. It featured journey planning, bus searches, displaying live times of buses, buying tickets, and more, with a strong emphasis on security. Payments were processed with the use of Braintree API and optional Apple Pay. I was a part of the two-person team, and later on, I became the lead iOS developer in the project. The app used flow controllers for navigation and observers for synchronizing data between managers and view controllers. Later, we moved from observers to the RxSwift ReactiveX library. Communication between the client and the back end was secured with OAuth authentication.

  • Meditation App

    A Swift-based app for meditation in VR.

    I was responsible for creating:
    • Community section
    • Data analysis section
    • Notifications section
    • Rewards sections

    Besides that, I also implemented a new home screen, refactored AV playback throughout the app, and unity integration in the project.

  • Audio Transmission App

    This app was created for my master's thesis. Its purpose was to transmit audio between two iOS devices with the least possible delay. For communication between devices, I used a hotspot made on one of them. The application consisted of many languages: C++ (Boost.Asio for socket networking and low-level audio operations), Objective-C++ (layer connecting C++ core and the Objective-C management layer), Objective-C (main audio session configuration and management), and Swift (application UI).

  • Flooring App

    This app was my research about the advanced usage of augmented reality on iOS. Its purpose was to replace flooring in real time. I used a mix of built-in panes detection mechanisms with a 3D voxels grid to mask 3D objects on a floor.

  • iOS App for a Global Biopharmaceutical Company

    This app was an internal tool to help with communication inside the company.
    I was the lead iOS developer in this project. It was written in Swift with the usage of the RxSwift ReactiveX library.
    What's more, I also developed a back end for this project. I did it in Swift with the usage of the Vapor 2 framework and deployed it on AWS. Communication between the client and back end was secured with Oauth authentication.

  • iOS App for Arris

    The purpose of the app was to help cable technicians and installation engineers. It contained an extensive database of guides and calculators that helped in everyday jobs. I was the lead developer in the project, and my responsibility was to create an iPad interface for the application and fix bugs. Communication between the client and the back end was secured with OAuth authentication.

  • iOS App for Gift Card Granny

    The app was built for a big gift card hub company in the US. It aggregated various discount gift card deals and gave users the best deal.
    I was the lead developer responsible for app development. It originally was written in Objective-C, and later on, new features were added in Swift. Communication between the client and back end was secured with Oauth authentication.

  • iOS App for Portafill

    The app was built for a big producer of construction equipment for internal uses. The app was to help salespeople do their job on-site. It featured marketing and technical content that could save for offline use.
    I was the only developer on the project and made this app from scratch. It was written in Objective-C. Communication between the client and the back end was secured with OAuth authentication.

  • eTabu

    A Swift-based word game with principles based on Taboo. The card decks were available in multiple languages, making the app viable as a party game and a teaching tool. Language schools were the app's primary target, which was supposed to bring some fun alternatives for regular learning sessions.


  • Languages

    Swift, Objective-C, GraphQL, SAML, C++, C, Java
  • Frameworks

    Core Location, UIKit, MapKit, iOS SDK, SwiftUI, Core Data, AudioUnit, Viper, Spring, OAuth 2, JPA, Hibernate, Spring Boot, Boost, Redux, Vapor, ARKit, iOS SceneKit
  • Libraries/APIs

    RxSwift, Alamofire, REST APIs, Fabric, Lottie-iOS, iOS Charts, CocoaPods, iOS API, ReactiveX, Firebase iOS SDK, AVKit, Sockets
  • Tools

    Xcode, Slack, Git, Apple Push Notifications, GitHub, Bitbucket, Charles Proxy, Braintree SDK, AWS AppSync, Unity SDK, Postman, Jira, Figma
  • Paradigms

    Agile Software Development, Concurrent Programming, Reactive Programming, Design Patterns, Model View Viewmodel (MVVM), REST, Model View Controller (MVC), Continuous Delivery (CD), Continuous Integration (CI), Scrum, Testing, VIPER Architecture, Agile, Unit Testing
  • Platforms

    iOS, MacOS, Bitrise, Keychain, Firebase, Docker, Amazon Web Services (AWS), AppsFlyer, AWS Elastic Beanstalk
  • Storage

    JSON, PostgreSQL, SQLite
  • Other

    GitFlow, Hockey, Flow Coordinators, Carthage, Lottie, WebKit, BrainTree, Objective-C++, GCD, SAML-auth, UDP, Payment APIs, CI/CD Pipelines, Reverse Engineering, Streaming


  • Master of Science Degree in Computer Science
    2012 - 2018
    University of Science and Technology - Cracow, Poland

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