Jacek Szyja, Developer in Swinoujscie, Poland
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Jacek Szyja

Verified Expert  in Engineering

Software Developer

Location
Swinoujscie, Poland
Toptal 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.

Portfolio

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

Experience

Availability

Part-time

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.

Work Experience

iOS Engineer

2020 - PRESENT
Self-employed
  • 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 that impact the end user experience the most.
  • Implemented Marcus' fast track flow, making 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
HYD
  • 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.
  • Provided consultation regarding 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
Softnauts
  • 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
MeduTools
  • 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

https://apps.apple.com/us/app/marcus-by-goldman-sachs/id1489511701
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

https://www.greggs.co.uk/app
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

https://librarysimplified.org
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

https://www.canon.pl/apps/photo-companion/
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

https://www.flowly.world
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

https://etabu.xyz/en/
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, iOS Native Libraries, 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), Mobile Development, Scrum, Testing, VIPER Architecture, Agile, Unit Testing

Platforms

iOS, MacOS, Bitrise, Keychain, Firebase, Mobile, 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, Algorithms, APIs, Maps, SAML-auth, UDP, Payment APIs, CI/CD Pipelines, Reverse Engineering, Streaming

2012 - 2018

Master of Science Degree in Computer Science

University of Science and Technology - Cracow, Poland

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