Juraj Kusnier, Developer in Munich, Bavaria, Germany
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Juraj Kusnier

Verified Expert  in Engineering

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.

Portfolio

Mawdoo3 Ltd
Flutter, Cross-platform, Mobile Applications, Live Chat, Go, Android, iOS...
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...

Experience

Availability

Part-time

Preferred Environment

MacOS, IntelliJ IDEA, 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

Full-stack (Flutter/Go) Developer

2023 - 2023
Mawdoo3 Ltd
  • Spearheaded the creation of a cutting-edge, chat-based, cross-platform mobile application from the ground up, serving as the foundation for a robust MVP project.
  • Orchestrated the development of a comprehensive API framework and successfully integrated it with a dynamic back-end solution, ensuring the seamless connection of mobile clients with a custom AI model and the powerful GPT-4 API.
  • Demonstrated exceptional efficiency by delivering polished, production-ready solutions within an extremely demanding timeframe, showcasing my ability to thrive under pressure.
Technologies: Flutter, Cross-platform, Mobile Applications, Live Chat, Go, Android, iOS, Google Cloud, Artificial Intelligence (AI), Machine Learning, Microservices, Docker, Minimum Viable Product (MVP), OpenAI GPT-4 API, Single Sign-on (SSO), Google Sign-in, Protobuf, gRPC, SDKs, Agile, PostgreSQL, Full-stack

Senior Android Developer

2022 - 2022
Trade Republic Bank GmbH
  • Implemented critical features that streamlined credit card processing, contributing to the application's financial efficiency.
  • Elevated the mobile app's overall user experience and interface using the latest technologies, such as Jetpack Compose, to ensure a modern and user-friendly design.
  • Strategically executed multiple successful A/B tests, significantly increasing app engagement and user retention rates.
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, Mobile Development, Front-end, CircleCI, Testing, Mobile Applications, Mobile Apps, SDKs, Agile

Senior Android Developer

2021 - 2022
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, Mobile Development, Front-end, CircleCI, Testing, Mobile Applications, Mobile Apps, SDKs, Agile, Barcode Reader

Android Developer

2018 - 2020
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, Mobile Development, Front-end, CircleCI, Testing, Mobile Applications, Mobile Apps, Maps, SDKs, Google Maps SDK, Google Maps API, Google Maps, Agile, PostgreSQL, ML Kit, Full-stack

Lead Mobile Developer

2015 - 2018
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, Mobile Development, Camera2 API, Minimum Viable Product (MVP), Front-end, Testing, Mobile Applications, Mobile Apps, SDKs, Agile, PostgreSQL, Full-stack, FlutterFlow, OpenGL, AI-generated Video

Android Developer

2014 - 2015
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, Mobile Development, Front-end, Testing, Mobile Applications, Mobile Apps, SDKs

Software Developer

2013 - 2014
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 Players, Digital Rights Management (DRM), Roku, Widevine, REST APIs, Video on Demand (VOD), Video Streaming, Networking, Web Development, Front-end, Testing, Mobile Apps, Android TV, IPTV, tvOS

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, which is 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 is an open-source Android app that implements the Media app architecture guidelines. It utilizes the Android MediaPlayer component to enable playback of audio files from the assets folder. With compatibility across Android phones, Android Auto, and Android Automotive OS (AAOS), the app offers a versatile audio playback experience. Its open-source nature invites community contributions and promotes transparency and innovation in its development.

Security Camera App with WebRTC

https://github.com/jurajkusnier/security-camera-demo
The project involves developing a security camera Android app that utilizes WebRTC, Jetpack Compose, and Kotlin. The app's primary purpose is to provide a security camera monitoring solution using local network connectivity without requiring an internet connection.

WebRTC Integration: The app leverages WebRTC technology to establish real-time communication and video streaming between two Android devices. The first one works as a server and broadcasts the video stream from the camera. The second one works as a client and receives a video signal from the first device. This enables efficient and secure video and audio data transmission over the local network.

Signaling Server with Node.js: A signaling server implemented using Node.js establishes connections and facilitates communication between mobile apps. This server acts as a mediator, handling signaling messages and facilitating the initiation of WebRTC sessions.

Background Video in Jetpack Compose - Demo Project

https://github.com/jurajkusnier/jetpack-login-screen
The project is an open-source Android app that showcases the usage of background video in Jetpack Compose. The app leverages the ExoPlayer library to seamlessly display an endless video stream as a background element behind other UI components on the login screen.

The project's main focus is to demonstrate how Jetpack Compose can be used to create visually engaging user interfaces where a dynamic video plays in the background, enhancing the overall aesthetics of the app.

By integrating the ExoPlayer library, the app achieves smooth and uninterrupted video playback, providing a visually immersive experience to users. The endless video stream ensures that the background video remains captivating and engaging without interruptions or noticeable repetitions.

The login screen is a primary use case for demonstrating this feature, as it is often the first point of interaction for users. The background video adds a visually appealing touch to the login screen, creating a more captivating and memorable user experience.
2008 - 2011

Bachelor's Degree in Information Technology

Slovak University of Technology - Bratislava, Slovakia

Libraries/APIs

RxJava, RxJava 2, REST APIs, Google Maps SDK, Google Maps API, Google Maps, OpenGL, Retrofit 2, Google AdSense, WorkManager API, Protobuf, Camera API, TensorFlow, Android API, Material 2, WebRTC, Camera2 API

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, CircleCI, ExoPlayer

Frameworks

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

Paradigms

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

Languages

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

Platforms

iOS, Android, Mobile, Android TV, FlutterFlow, Firebase, Amazon Web Services (AWS), DigitalOcean, Docker, Android Automotive, tvOS

Storage

Databases, PostgreSQL, Elasticsearch, SQLite, RoomDB, Amazon S3 (AWS S3), JSON, Google Cloud

Industry Expertise

Telecommunications

Other

Android Development, Over-the-top Content (OTT), Mobile App Development, Networking, Front-end, Mobile Applications, Mobile Apps, Jetpack Compose, User Interface (UI), A/B Testing, Coroutines, Subscriptions, Kotlin Multiplatform Mobile (KMM), APIs, User Experience (UX), HTTP, Authentication, Integration, Android Architecture, Android Animations, VoIP, Audio Streaming, Video Streaming, Minimum Viable Product (MVP), Maps, SDKs, Full-stack, Computer Networking, Informatics, Software Development, Material Design, Open Source, Room, Hilt, Google Play Store, App Store, Google AdMob, In-app Purchases, Java Native Interface (JNI), Smart TV, Digital Rights Management (DRM), Exposure Notification System, Machine Learning, CI/CD Pipelines, Push Notifications, Code Review, Source Code Review, Data Encryption, UI Testing, 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, Web Development, Open-source Software (OSS), MVP Design, Videos, Video Players, Live Chat, Artificial Intelligence (AI), OpenAI GPT-4 API, Single Sign-on (SSO), Google Sign-in, Barcode Reader, ML Kit, IPTV, AI-generated Video

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