Juraj Kusnier, Developer in Munich, Bavaria, Germany

Juraj Kusnier

Android Developer

Location
Munich, Bavaria, Germany
Toptal Member Since
November 9, 2022

Juraj is an experienced senior software engineer and Android app developer focusing on products and a high-quality user experience. In the last 10+ years, he worked on critical projects for small and large clients, banks, and government agencies and shipped apps for tens of millions of users. Juraj knows how to deal with large legacy systems and quickly and effectively set up and launch greenfield apps.

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Portfolio

Trade Republic Bank GmbH
Android Development, Jetpack Compose, Model View Intent (MVI), RxJava 2...
SAP
Kotlin, Coroutines, Android Jetpack, Model View Viewmodel (MVVM), Dagger 2...
Holidu
Java, Kotlin, Model View Viewmodel (MVVM), Firebase, Hilt, Dependency Injection...

Experience

Java - 10 yearsAndroid - 10 yearsAndroid Development - 10 yearsKotlin - 5 yearsCoroutines - 4 yearsModel View Intent (MVI) - 2 yearsJetpack Compose - 2 yearsKotlin Multiplatform Mobile (KMM) - 2 years

Location

Munich, Bavaria, Germany

Availability

Full-time

Preferred Environment

MacOS, IntelliJ, Android Studio, Git

The most amazing...

...project I’ve worked on is the official Corona-Warn-App for Germany, which helped slow down the spread of COVID-19 infections and most likely saved many lives.

Work Experience

2022 - 2022

Senior Android Developer

Trade Republic Bank GmbH
  • Implemented critical features for credit card processing.
  • Improved the overall UI and UX of a mobile app using the latest technologies, such as Android Jetpack.
  • Implemented multiple successful A/B tests. Increased app engagement and user retention.
Technologies: Android Development, Jetpack Compose, Model View Intent (MVI), RxJava 2, Firebase, Material Design, Kotlin, Android Material Design, User Interface (UI), Model View Viewmodel (MVVM), GitHub, Dagger 2, Dependency Injection, A/B Testing, Android, CI/CD Pipelines, Continuous Integration (CI), Continuous Delivery (CD), SonarQube, Code Review, Source Code Review, Gradle, Git, Unit Testing, Mockito, Android Jetpack, Android Studio, User Experience (UX), Mobile App Development, Mobile, REST APIs, Test-driven Development (TDD), Behavior-driven Development (BDD), Figma, Databases, RxJava, Networking
2021 - 2022

Senior Android Developer

SAP
  • Developed an app that helps trace infection chains of SARS-CoV-2 (which can cause COVID-19). Used the exposure notification API from Apple and Google.
  • Implemented and maintained critical features according to the requirements of the German government.
  • Created an automated screenshots pipeline using Firebase, which handled multiple languages and screen configurations.
  • Maintained an open-source project and took care of open issues and PR reviews.
Technologies: Kotlin, Coroutines, Android Jetpack, Model View Viewmodel (MVVM), Dagger 2, Open Source, Notification Center, Room, Retrofit 2, JSON Web Tokens (JWT), GitHub, RoomDB, Gradle, Material Design, Android Material Design, WorkManager API, Data Encryption, Continuous Delivery (CD), Continuous Integration (CI), CI/CD Pipelines, Git, Unit Testing, UI Testing, JUnit, Mockito, Espresso, Android Studio, IntelliJ IDEA, REST, APIs, User Experience (UX), Protobuf, Camera API, QR Codes, Bluetooth, Fastlane, Mobile App Development, Mobile, REST APIs, Test-driven Development (TDD), Behavior-driven Development (BDD), Figma, Databases, RxJava, Networking
2018 - 2020

Android Developer

Holidu
  • Developed many challenging features like login, in-app bookings, and a theme-based search. Increased app engagement and overall app revenue.
  • Implemented image classification using machine learning running on mobile devices during the company hackathon.
  • Designed and implemented multiple REST APIs endpoints and microservices using the Spring Boot framework.
  • Migrated the legacy Java code base to Kotlin and increased testability, app stability, and test coverage.
  • Cleaned the app architecture and introduced dependency injection to the project.
Technologies: Java, Kotlin, Model View Viewmodel (MVVM), Firebase, Hilt, Dependency Injection, Retrofit 2, REST, Elasticsearch, Grafana, Kibana, A/B Testing, Android, Android Development, Android Jetpack, Android Material Design, Android Studio, APIs, API Design, Back-end, Back-end Development, Amazon Web Services (AWS), Amazon S3 (AWS S3), Spring Boot, IntelliJ IDEA, JSON, Git, GitHub, Gradle, Machine Learning, Image Recognition, TensorFlow, User Experience (UX), Unit Testing, Integration Testing, Microservices, Scrum, Mobile App Development, Mobile, REST APIs, Android Animations, Test-driven Development (TDD), Behavior-driven Development (BDD), Figma, Databases, RxJava, Networking
2015 - 2018

Lead Mobile Developer

Verusoft
  • Led a small team of programmers and designers. Built multiple successful mobile apps and games with more than 3,000,000 downloads and positive user reviews.
  • Worked closely with the Android Instant Apps as an early adopter. Worked with Google on implementing this feature.
  • Handled the entire software development life cycle, from the idea to the app design, implementation, launch, marketing, and maintenance.
Technologies: Android Development, iOS, Unity SDK, Java, JavaScript, Google Play Store, App Store, App Store Optimization (ASO), Google AdSense, Google AdMob, In-app Purchases, Subscriptions, Flutter, Dart, Cross-platform, Cross-platform App Development, APK, Firebase, Crashlytics, Unit Testing, User Interface (UI), Android, Android SDK, Android API, Android Studio, Gradle, Game Design, Game Development, Team Leadership, Unity3D, DigitalOcean, A/B Testing, Mobile App Development, Mobile, REST APIs, Android Animations, Test-driven Development (TDD), Behavior-driven Development (BDD), Databases, Audio Streaming, RxJava, Video Streaming, WebSockets, WebRTC, Networking
2014 - 2015

Android Developer

Foundation
  • Worked on an Android client for one of the first B2B file synchronization platforms called Soonr Go, Acquired by Autotask Corporation.
  • Built the front end of an Android app using a synchronization library written in C++.
  • Accomplished big refactoring and a migrated legacy C++ core library to Java.
Technologies: Java, Android NDK, Java Native Interface (JNI), C++, Subversion (SVN), Git, SQLite, C, Android SDK, Android Studio, Unit Testing, JUnit, Jenkins, Encryption, Data Encryption, Cross-platform, Cross-platform Libraries, Cross-platform App Development, File Sharing, CI/CD Pipelines, Continuous Integration (CI), Continuous Delivery (CD), B2B, Mobile App Development, Mobile, REST APIs, Test-driven Development (TDD), Behavior-driven Development (BDD), Databases, JNI, Networking
2013 - 2014

Software Developer

Siemens Convergence Creators (Atos)
  • Developed a multi-platform service for smart TV and web.
  • Implemented digital rights management to manage legal access to digital content.
  • Led the migration of a multi-media streaming service from the web to various smart TV devices.
Technologies: JavaScript, CSS, HTML, AngularJS, Smart TV, Over-the-top Content (OTT), Media Player, Digital Rights Management (DRM), Roku, Widevine, REST APIs, Video on Demand (VOD), Video Streaming, Networking

Experience

Trade Republic: an Android Mobile Broker App

https://traderepublic.com/
Trade Republic Bank GmbH is a German online broker in Berlin. It allows shares, derivatives, and cryptocurrencies to be traded on its mobile app.

I worked for Trade Republic as a freelance mobile developer together with a big team of internal developers. I implemented multiple successful experiments and improved the overall UI and UX of the mobile app using the latest technologies, such as Jetpack Compose.

Holidu: an Android Accommodation App

https://www.holidu.com/
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. The app makes millions of travelers happy by helping them book the ideal accommodation for the lowest price.

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

Corona-Warn-App: an Android Coronavirus App

https://www.coronawarn.app/en/
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, which 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 a freelance developer 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 helped many people and most likely saved some lives.

Nature and Relaxing Sounds

https://github.com/jurajkusnier/relaxing-sounds
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, Android Auto, and the new Android Automotive OS (AAOS).

Skills

Languages

Kotlin, Java, JavaScript, Dart, C++, C, CSS, HTML

Frameworks

Flutter, Android SDK, JNI, Dagger 2, JSON Web Tokens (JWT), AngularJS, Media Player, Mockito, JUnit, Spring Boot, Unity3D

Libraries/APIs

RxJava, RxJava 2, REST APIs, Retrofit 2, Google AdSense, WorkManager API, Protobuf, Camera API, TensorFlow, Android API, Material 2, WebRTC

Platforms

Android, Mobile, Firebase, iOS, Amazon Web Services (AWS), DigitalOcean

Other

Android Development, Mobile App Development, Networking, Jetpack Compose, User Interface (UI), Coroutines, Subscriptions, Kotlin Multiplatform Mobile (KMM), APIs, User Experience (UX), HTTP, Authentication, Integration, Android Architecture, Android Animations, VoIP, Audio Streaming, Video Streaming, Computer Networking, Informatics, Software Development, Material Design, A/B Testing, Open Source, Room, Hilt, Google Play Store, App Store, Google AdMob, In-app Purchases, Java Native Interface (JNI), Smart TV, Over-the-top Content (OTT), Digital Rights Management (DRM), Exposure Notification System, Machine Learning, CI/CD Pipelines, Push Notifications, Code Review, Source Code Review, Data Encryption, UI Testing, Espresso, QR Codes, Bluetooth, API Design, Back-end, Back-end Development, Image Recognition, Integration Testing, Cross-platform App Development, APK, Game Design, Game Development, Team Leadership, Encryption, Cross-platform Libraries, File Sharing, Roku, Widevine, QA Testing, OAuth, SSL, SSL Certificates, Video on Demand (VOD), Audio, Notification Center, WebSockets

Tools

Git, Android Studio, GitHub, Android Jetpack, Grafana, Kibana, Unity SDK, Android NDK, Subversion (SVN), Jenkins, SonarQube, Gradle, IntelliJ IDEA, Fastlane, Crashlytics, Android Auto, Figma

Paradigms

Model View Intent (MVI), Model View Viewmodel (MVVM), Test-driven Development (TDD), Behavior-driven Development (BDD), Design Patterns, Android Material Design, Dependency Injection, REST, App Store Optimization (ASO), Continuous Integration (CI), Continuous Delivery (CD), Unit Testing, Microservices, Cross-platform, B2B, Scrum

Storage

Databases, Elasticsearch, SQLite, RoomDB, Amazon S3 (AWS S3), JSON

Industry Expertise

Telecommunications

Education

2008 - 2011

Bachelor's Degree in Information Technology

Slovak University of Technology - Bratislava, Slovakia