Bohdan is available for hire

Bohdan Varchenko

Verified Expert in Engineering

Mobile Developer

Kyiv, Ukraine

Toptal member since December 27, 2021

Expertise

Android SDK Git Android Kotlin Software Development JUnit Bluetooth Java REST API Firebase JavaScript Realm Flutter

Bio

Bohdan is a hardworking IT professional with 7+ years of experience as an Android developer. He holds a master's degree in computer science and a genuine passion for technology, particularly mobile applications' development. Bohdan's been building applications from scratch and with an existing codebase—by himself, as a part of a team, and as a team leader—working with multiple libraries, APIs, and methodologies.

Portfolio

Nanoleaf

Android, Java, Kotlin, Realm

Svitla Systems

Android SDK, Android Architecture Components, Kotlin, Dagger 2, Scrum, Git...

Perenio IoT

Android SDK, RxJava, WebSockets, SQLite, Kotlin, Java, Scrum, Git...

Experience

Android - 7 years
Git - 7 years
Android SDK - 7 years
Kotlin - 5 years
RxJava - 4 years
SQLite - 4 years
JUnit - 3 years
Android Architecture Components - 2 years

Availability

Part-time

Preferred Environment

Android Studio, Visual Studio Code (VS Code), Linux, MacOS, Kotlin, Java, Android SDK

The most amazing...

...thing I've developed is an Android application that dynamically gets data updates over a WebSocket and uses Geolocation and User Activity APIs.

Work Experience

Senior Android Developer

2022 - 2022

Nanoleaf

Refactored part of the codebase into MVVM pattern following clean architecture principles for Nanoleaf, an IoT company.
Improved performance of Realm database interaction using separate threads and subscriptions.
Implemented new features and fixed bugs using agile tracking tools.

Technologies: Android, Java, Kotlin, Realm

Android Developer

2020 - 2021

Svitla Systems

Developed an app with a multi-module architecture following clean architecture principles, using Kotlin and Coroutines.
Worked within the agile framework and used Jira as a reporting tool.
Followed a GitFlow approach to enhance team collaboration and parallel work on new features.

Technologies: Android SDK, Android Architecture Components, Kotlin, Dagger 2, Scrum, Git, Object-oriented Programming (OOP), Gang of Four (GOF) Design Patterns, Coroutines, JUnit, Espresso, GraphQL, Android, Android Studio, RxJava 2, Mobile, Gradle, Model View ViewModel (MVVM), Retrofit 2, Mobile App Development, Android Jetpack, Retrofit, LiveData, Firebase

Android Developer

2019 - 2020

Perenio IoT

Built an architecture for an Android application following clean architecture principles.
Configured a WebSocket connection and instant UI updates, caching all data when new data arrived.
Covered the main components of the application with unit tests and integration tests.

Technologies: Android SDK, RxJava, WebSockets, SQLite, Kotlin, Java, Scrum, Git, Object-oriented Programming (OOP), Gang of Four (GOF) Design Patterns, Android Architecture Components, Dagger 2, JUnit, Espresso, REST APIs, Android, Android Studio, RxJava 2, Mobile, Gradle, Model View ViewModel (MVVM), Bluetooth, Retrofit 2, Mobile App Development, Android Jetpack, Retrofit, LiveData, Firebase

Senior Android Developer

2018 - 2019

Innovecs

Developed and supported Android components for a React Native application.
Worked with an agile framework and used Jira as a reporting tool.
Followed a GitFlow approach to enhance team collaboration and parallel work on new features.

Technologies: Android SDK, Kotlin, Git, JavaScript, React Native, Java, Object-oriented Programming (OOP), Gang of Four (GOF) Design Patterns, Scrum, Android, Android Studio, Mobile, Gradle, Mobile App Development

Android Developer

2017 - 2018

Pokupon

Developed an application with Google Maps, geolocation, and REST APIs.
Implemented clean architecture principles from scratch. Separated all data flows into three layers capable of interacting with interfaces.
Covered the essential parts of the application with tests.

Technologies: Android SDK, RxJava, SQLite, Kotlin, Scrum, Git, Object-oriented Programming (OOP), Gang of Four (GOF) Design Patterns, Dagger 2, REST APIs, JUnit, Android, Android Studio, RxJava 2, Realm, Retrofit 2, Mobile, Gradle, Mobile App Development, Retrofit, Firebase

Android Developer

2017 - 2017

Syndicode

Developed several Android applications from scratch using mobile development best practices.
Mentored a junior iOS developer in mobile development specification.
Worked alongside the project manager to improve the team's communication.

Technologies: Java, Kotlin, SQLite, RxJava, Scrum, Git, Object-oriented Programming (OOP), Dagger 2, REST APIs, Android, Android Studio, Retrofit 2, Realm, Mobile, Gradle, Android SDK, Mobile App Development, Retrofit, Firebase

Android Developer

2016 - 2017

Digital Hanger

Implemented a C++ Android library for WebSocket communication with the server.
Connected the mobile library through a Node.js server application.
Investigated how to implement UDP hole punching in Android applications.

Technologies: Java, Android SDK, WebSockets, Git, JavaScript, Android NDK, Android, Android Studio, Mobile, Gradle, Mobile App Development

Android Developer

2014 - 2016

4-com

Created and provided support to several Android applications from scratch.
Tracked and fixed features and bugs using Jira as a reporting tool.
Learned Android SDK and then conducted other developers throughout the first steps.

Technologies: Java, Android SDK, SQLite, Git, Scrum, Object-oriented Programming (OOP), REST APIs, Android, Android Studio, Mobile, Gradle, Mobile App Development

Experience

Nanoleaf

https://play.google.com/store/apps/details?id=me.nanoleaf.nanoleaf

A Kotlin-based Android application for the configuration and management of Nanoleaf IoT products. The app uses Bluetooth and a local network to interact with accessories. As an Android developer, I took part in refactoring the codebase to follow clean architecture principles and MVI architecture. Also, I optimized database interaction using parallel threads created by Kotlin coroutines and Kotlin flows.

Travel Guidance Android Application (NDA)

The world's largest travel platform helps 463 million travelers each month make every trip their best trip. Travelers across the globe use the client site and app to browse more than 859 million reviews and opinions of 8.6 million accommodations, restaurants, experiences, airlines, and cruises. Whether planning or on a trip, travelers turn to companies to compare low prices on hotels, flights, and cruises, book popular tours and attractions, as well as reserve tables at great restaurants. The company, the ultimate travel companion, is available in 49 markets and 28 languages.

Technology stack: Kotlin, Coroutines, Kotlin Flow, Hilt/Dagger2, Retrofit 2, GraphQL, Android Jetpack (Navigation, LiveData), and Epoxy in a modular layout that follows SOLID principles using Clean Architecture with MVVM.

Perenio Smart: Building Management System

https://play.google.com/store/apps/details?id=com.perenio.smarthome

The Smart Home Project by Perenio IoT is a packaged solution for home management and security, operated via a mobile application.

I built the Android application based on Clean Architecture principles with Kotlin, RxJava, and WebSockets. The app has an offline mode, implemented with SQLitethe, that allows it to show cached data when the user has no internet connection. Finally, the main parts of the application were covered with unit tests and integration tests. This resulted in a flexible and maintainable application.

Food Delivery Application (NDA)

A food delivery marketplace application where users can discover the nearest restaurants and order any food. The app shows general information about restaurants and food provided by owners. Also, users put ratings on previous orders and see ratings from other customers.

Personal Stuff Transport Application (NDA)

The app is an on-demand marketplace where individuals needing moving services can price their moves and instantly connect with truck owners around town. The app allows a user to register as a driver or customer. Truck drivers can see the nearest available customer requests with details and apply for them. Requests can be represented as a list or as pins on a map. Customers can see their current and previous requests and see a detailed view of the previous offers.

Education

2014 - 2015

Master's Degree in Computer Science

V.N. Karazin Kharkiv National University - Kharkiv, Ukraine

2009 - 2014

Bachelor's Degree in Computer Science

Kharkiv National University of Radio Electronics - Kharkiv, Ukraine

Certifications

MARCH 2023 - PRESENT

The Complete Flutter Development Bootcamp with Dart

Udemy

Skills

Libraries/APIs

RxJava, Android Architecture Components, REST APIs, Retrofit 2, RxJava 2, Retrofit, LiveData, Google Maps SDK

Tools

Git, Android Studio, Gradle, Android Jetpack, Android NDK

Languages

Kotlin, Java, JavaScript, Dart, GraphQL

Frameworks

Android SDK, Dagger 2, JUnit, Espresso, Flutter, React Native

Paradigms

Object-oriented Programming (OOP), Gang of Four (GOF) Design Patterns, Scrum, Model View ViewModel (MVVM)

Platforms

Android, Mobile, Firebase

Storage

SQLite, Realm

Other

Mobile App Development, WebSockets, Coroutines, Bluetooth, Mobile GPS

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