Janos is available for hire
Hire JanosJanos Breuer
Verified Expert in Engineering
Android Developer
Budapest, Hungary
Toptal member since June 28, 2016
Bio
Janos has 12+ years of experience specializing in building successful mobile apps for diverse industries, including finance, SaaS, and AI. His proficiency extends to mobile DevOps and automation. He created a comprehensive mobile advisory platform for Forex traders and a remote collaboration app with over 1 million installs at a Forbes Fast Tech 25 company. Janos is a skilled and communicative developer who prioritizes simplicity, excellent user experience, and cost-efficiency in his projects.
Portfolio
Realeyes
SWIG, Android NDK, Amazon Kinesis, Retrofit, KOIN, Kotlin, Android, Coroutines...
W.UP
JUnit, Mockito, Jenkins, Kodein, KOIN, Dagger 2, Retrofit 2, Kotlin, Android...
LogMeIn
WebRTC, JNI, Mockito, Guice, Retrofit, Android SDK, Dagger, Android Studio...
Experience
Availability
Part-time
Preferred Environment
Windows, Git, Android Studio, Java, Kotlin, GitHub, Android
The most amazing...
...app I've created is a real-time trading advisory platform for Android and iOS, integrated with 3rd-party broker APIs.
Work Experience
Senior Mobile Developer
2020 - 2023
Realeyes
- Implemented a digital well-being app with Jetpack Compose UI and clean architecture.
- Wrote a wrapper SKD for a native emotion detection component.
- Implemented REST API session handling and integrated Amazon Kinesis SDK.
- Designed RxJava interfaces for internal components of the SDK.
Technologies: SWIG, Android NDK, Amazon Kinesis, Retrofit, KOIN, Kotlin, Android, Coroutines, Jetpack Compose, Kotlin Multiplatform, Swagger, Android Studio, Test-driven Development (TDD), Android SDK, JUnit, Design Patterns, Unit Testing, JPA, Gradle, REST, Dependency Injection, JNI, Retrofit 2, Automation, SDKs, Clean Architecture, RxJava 2, Firebase, Push Notifications, REST APIs, APIs
Senior Mobile Developer
2017 - 2020
W.UP
- Developed mobile banking Android applications for several European banks, e.g., Cembra.
- Built complex UIs with theming, as well as the foundation of the business logic, so that it adheres to clean architecture.
- Integrated a mobile payment service to one of the apps.
- Held test-driven development presentations and workshops for my team.
Technologies: JUnit, Mockito, Jenkins, Kodein, KOIN, Dagger 2, Retrofit 2, Kotlin, Android, Dagger, Android Studio, Test-driven Development (TDD), Android SDK, Retrofit, Spring, Spring Boot, Spring MVC, Design Patterns, Unit Testing, Gradle, REST, Dependency Injection, Automation, Clean Architecture, RxJava 2, Firebase, Push Notifications, Technical Leadership, REST APIs, APIs
Android Developer
2014 - 2016
LogMeIn
- Developed two apps and an SDK for Android as part of the mobile scrum team at LogMeIn Rescue. These applications are integral components of a large-scale SaaS application used for remote support by companies like Microsoft and Vodafone.
- Used a wide range of Android system features to remotely control and diagnose a device.
- Refactored the remote control component so that it could be unit-tested.
Technologies: WebRTC, JNI, Mockito, Guice, Retrofit, Android SDK, Dagger, Android Studio, Test-driven Development (TDD), JUnit, Android NDK, Design Patterns, Unit Testing, Gradle, REST, Dependency Injection, Dagger 2, Retrofit 2, Automation, SDKs, REST APIs, APIs
Full-stack Developer
2011 - 2016
MuTrader.com
- Developed a real-time financial mobile app for iOS and Android with a back-end server that had push notifications and an integration to 3rd-party Forex broker systems.
- Implemented the back end with service-oriented architecture and a RESTful API.
- Used enterprise integration patterns and FIX protocol to connect to brokers.
- Wrote unit tests and automated acceptance tests with TDD.
Technologies: QuickFIX, Xamarin, FIX Protocol, AngularJS, Play Framework, Apache Camel, Hibernate, Spring, Mockito, JUnit, Dagger 2, Retrofit, Android SDK, Android Studio, Test-driven Development (TDD), Spring Boot, Spring MVC, C#, Xamarin.iOS, YAML, JavaScript, iOS, Design Patterns, Unit Testing, JPA, Enterprise Integration Patterns (EIP), REST, Dependency Injection, Angular, MySQL, Azure, Push Notifications, Technical Leadership, REST APIs, API Integration, APIs, Trading, Profit & Loss (P&L), Trading Systems, Finance APIs, Brokers, Finance
Lead Software Engineer
2011 - 2013
LogMeIn
- Led a team of 7-9 engineers in the development of two Windows client components for LogMeIn Rescue.
- Acted as a member of the company-wide architecture review board.
- Interviewed new developer candidates and participated in the hiring decisions.
- Created a code-branching policy and introduced code reviews, which stabilized the release process of the component.
- Evangelized unit-testing and test-driven development (TDD); also organized TDD training sessions for the team.
- Created the system design and a prototype for the planned rewrite of a client component for four platforms (Windows, Mac, Android, and iOS).
Technologies: SOAP, Win32 API, ATL, Standard Template Library (STL), C++, Netscape Plugin Application Programming Interface (NPAPI), Browser Plugins, Test-driven Development (TDD), Windows, UML, Design Patterns, Unit Testing, Wix, Win32, Technical Leadership, APIs
Software Engineer
2007 - 2011
LogMeIn
- Collaborated with the C++ team at LogMeIn Rescue to develop a browser plugin using SOAP, STL, and ATL.
- Implemented major features in the Windows component of the product, including technician collaboration and unattended access.
- Implemented a task-based threading model that allowed the team to eliminate frequent bugs related to deadlocks and UI freezes.
- Answered level 3 support requests, troubleshooting urgent technical issues with VIP customers.
- Presented to 100+ developers at a company conference about my team's achievements.
Technologies: Netscape Plugin Application Programming Interface (NPAPI), Win32 API, SOAP, ATL, Standard Template Library (STL), C++, Windows, UML, Design Patterns, Unit Testing, Browser Plugins, Win32, APIs
Software Engineer
2006 - 2007
Lufthansa Systems
- Developed an airline schedule optimizer in a distributed team, communicating daily with remote team members.
- Implemented and unit-tested graph data structures and algorithms in C++ on four Unix variants.
- Refactored our unit-testing framework, significantly reducing the size of unit test binaries and saving storage-related costs.
Technologies: Linux, Unix, C++, UML, Design Patterns, Unit Testing, Algorithms
Experience
Mindfully App
https://play.google.com/store/apps/details?id=com.realeyesit.mindfully&hl=en&gl=USCreated a digital well-being application with a user base exceeding 50,000 downloads, focused on monitoring and analyzing facial expressions during mobile phone usage to provide insights into the emotional impact of technology usage.
In this role, I spearheaded the rewrite of an SDK to encapsulate the image recognition component, facilitating emotion detection in 3rd-party apps.
Collaborating closely with a team of two developers, I introduced advanced theming techniques using Jetpack Compose. Additionally, I successfully advocated for the implementation of clean architecture principles, thereby ensuring the scalability and maintainability of the project.
In this role, I spearheaded the rewrite of an SDK to encapsulate the image recognition component, facilitating emotion detection in 3rd-party apps.
Collaborating closely with a team of two developers, I introduced advanced theming techniques using Jetpack Compose. Additionally, I successfully advocated for the implementation of clean architecture principles, thereby ensuring the scalability and maintainability of the project.
Cembra Mobile Bank
I developed the Android mobile bank client application for Cembra, a Swiss credit card bank.
I used state-of-the-art architecture and technologies in this project, such as biometric authentication, clean architecture, reactive programming, and dependency injection.
I used state-of-the-art architecture and technologies in this project, such as biometric authentication, clean architecture, reactive programming, and dependency injection.
LogMeIn Rescue
https://play.google.com/store/apps/details?id=com.logmein.rescuemobile&hl=huLogMeIn Rescue is a SaaS platform used by millions to get remote support from tech support companies and software vendors such as Microsoft and Vodafone. I worked on the Android app and the Windows client and designed several features as an architect.
As the lead developer of a team of 7-9 engineers, I implemented a code branching policy and pioneered a code review process. These initiatives improved code quality, enhanced knowledge sharing, and stabilized release processes for the component.
As the lead developer of a team of 7-9 engineers, I implemented a code branching policy and pioneered a code review process. These initiatives improved code quality, enhanced knowledge sharing, and stabilized release processes for the component.
Rescue Lens
https://play.google.com/store/apps/details?id=com.logmein.rescuelens&hl=huThe Rescue Lens app for Android allows support agents to use the camera on the user's Android device to see what they are seeing.
I implemented several features in the app and planned and performed a major refactoring that made the code more robust and maintainable.
I implemented several features in the app and planned and performed a major refactoring that made the code more robust and maintainable.
Stack Overflow Contributions
https://stackoverflow.com/users/5132200/janos-breuerAs a personal project, I answered several questions on Stackoverflow.com related to Android development. That allowed me to learn to express ideas in a clear and concise way, and also to learn more about specific topics related to Android development.
MuTrader
https://drive.google.com/file/d/1ghKMfI-Ty0uEZWN-PQOttVQ-D7Dui6z8/viewMuTrader is a financial mobile app for iOS and Android with a back-end server with push notifications and integration to 3rd-party Forex broker systems.
It connected Forex advisers, traders, and brokers.
It connected Forex advisers, traders, and brokers.
Education
2001 - 2006
Master's Degree in Mathematics
Budapest University of Technology and Economics - Budapest, Hungary
Skills
Libraries/APIs
Retrofit, RxJava 2, REST APIs, WebRTC, ATL, Win32 API, Retrofit 2, Standard Template Library (STL), Xamarin.iOS
Tools
Android Studio, Kodein, Gradle, Jenkins, Git, Android NDK, SWIG, Wix, GitHub
Languages
Java, Kotlin, C++, YAML, UML, C#, JavaScript, Bash Script
Frameworks
Android SDK, Dagger, Mockito, KOIN, Swagger, Spring Boot, Spring, AngularJS, Spring MVC, Apache Camel, Guice, JNI, Dagger 2, JUnit, Play Framework, JPA, Hibernate, Angular
Paradigms
REST, Test-driven Development (TDD), Design Patterns, Dependency Injection, Unit Testing, Automation, Clean Architecture
Platforms
Android, Windows, Linux, Firebase, Unix, Xamarin, iOS, Azure, Win32
Storage
MySQL
Industry Expertise
Trading Systems
Other
API Integration, APIs, Algorithms, Push Notifications, Technical Leadership, SOAP, Netscape Plugin Application Programming Interface (NPAPI), Amazon Kinesis, QuickFIX, Enterprise Integration Patterns (EIP), FIX Protocol, Mathematics, Coroutines, Jetpack Compose, Kotlin Multiplatform, Browser Plugins, SDKs, Trading, Profit & Loss (P&L), Finance APIs, Brokers, Finance
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