Juraj Kušnier

Trade Republic Bank GmbH is a German online broker in Berlin. Shares, derivatives, and cryptocurrencies can be traded on a mobile app.

I worked for Trade Republic as a freelance mobile developer together with a big team of internal developers. I worked on critical features for credit card processing and savings as well as on implementing multiple successful experiments and improved the overall UI and UX of the mobile app using the latest technologies, such as Jetpack Compose.

Technologies: Kotlin, Jetpack Compose, Model View Intent (MVI), RxJava, Firebase, Material Design, Model View Viewmodel (MVVM), GitHub, Dagger 2, Dependency Injection, CI/CD Pipelines, Unit Testing, Mockito, Android Jetpack, UX, and more

The Corona-Warn-App is an app that helps trace infection chains of SARS-CoV-2 (which can cause COVID-19) in Germany. The app is based on technologies with a decentralized approach and notifies users if they have been exposed to SARS-CoV-2. It is the main corona app for Germany, where it is interconnected with the national health care system. Great emphasis is placed on data protection and transparency since the mobile app handles the sensitive health data of users. The project is open-source and available on GitHub.

I worked on this project as an external contractor and helped to implement many features, tests, and bug fixes. Even though the project was challenging in many ways, it was also a great experience as we really helped many people and most likely saved some lives.

Technologies: Kotlin, Exposure Notification API, Coroutines, Material Design, Dagger 2, Room, Retrofit, WorkManager, DataStore, JWT, Bouncy Castle, and more

Holidu is one of the fastest-growing travel tech companies worldwide. It's based in Munich, Germany, and provides a vacation rental meta-search engine.

During more than 2 years in the company, I have converted the original Java codebase of the Holidu Android App to Kotlin, increased test coverage, cleaned the app architecture, and introduced dependency injection to the project. I developed many challenging features like google sign-in, theme-based search, or image classification using machine learning (hackathon project). I improved the look and feel of the app by implementing the Material design components, fancy transitions, and animations.

Technologies: Java, Kotlin, MVVM, MVI, RxJava, Retrofit, Room, Coroutines, Push-Notifications, Hilt, Firebase, Jenkins and more

Minesweeper is a mobile version of a well-known puzzle video game. The game has more than 2,000,000 downloads and very good user reviews. The objective of the game is to clear a rectangular board containing hidden "mines" or bombs without detonating any of them, with help from clues about the number of neighboring mines in each field.

I closely monitor the app with tools like firebase analytics to better understand how users use the app and crashlytics to quickly detect new issues. I use A/B testings and staged rollouts before publishing major changes and new features. One of the major features I've added to the app was Google Play Instant, where people can tap to try an app without installing it on their phones.

Technologies: Java, Kotlin, Firebase, AdMob, Google Play Instant, and more

Wealth Check allows you to check the balance and history of any bitcoin wallet. Just scan the bitcoin address QR code to see all important information like bitcoin balance, fiat balance by current conversation rate, transactions history, etc. All scanned wallets are safely stored on your phone for offline access. You can sort wallets in the favorites list.

The app is written in the Kotlin programming language. It's my open source project and the source code is available on GitHub. I have chosen the MVVM pattern for the main app structure. I have implemented part of Android Architecture Components and libraries like RxJava, Retrofit, Dagger 2, Moshi, etc. Feel free to contribute.

Technologies: Kotlin, Android Architecture Components, Hilt, Retrofit 2, Room, Moshi, Coroutines, and more

The project follows Media app architecture guidelines. It uses Android MediaPlayer to play audio files saved in the assets folder. Playback is available on Android Phones as well on Android Auto and the new Android Automotive OS.

The app is written 100% in Kotlin programming language. The project is open-source and available on GitHub.