Oleksandr Rabinovych, Developer in Svishtov, Bulgaria
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Oleksandr Rabinovych

Verified Expert  in Engineering

Android Developer

Svishtov, Bulgaria
Toptal Member Since
February 1, 2016

Oleksandr has developed many sophisticated Android projects as well as some web projects and apps for embedded systems. He is a talented, creative expert in his field who loves tasks requiring lateral thinking. He is also a quick study who loves tackling new tech. At the same time, Oleksandr is an easy-going and understanding person which greatly contributes to an enjoyable and cooperative work atmosphere when working with others.


iwinBACK Sales Inc.
Android, Mobile App Development, Telecommunications, SMS, Kotlin, Mobile, VCS
HypeLabs (via Toptal)
Android, Java, Bluetooth LE, Java Concurrency, Concurrent Programming, Mobile...
Kotlin, Android, Model View ViewModel (MVVM), Coroutines, SVG...




Preferred Environment

Mercurial, Git, Eclipse, Android Studio, Linux

The most amazing...

...project I've worked on was an Android client for a service which uses artificial intelligence to transform boring camera videos into exciting movies.

Work Experience

Senior Android Developer

2023 - 2023
iwinBACK Sales Inc.
  • Helped develop a protocol for client-server communication for the mobile app.
  • Developed an Android app to capture and sync SMS/call data.
  • Gave feedback on the database structure to improve its maintainability.
Technologies: Android, Mobile App Development, Telecommunications, SMS, Kotlin, Mobile, VCS

Android Developer

2022 - 2022
HypeLabs (via Toptal)
  • Developed an Android SDK in Java for creating mesh networks via BLE for facilitating internet transactions by devices with limited connectivity.
  • Implemented device disappearance and internet connectivity state propagation via a mesh network.
  • Stabilized the Java codebase by improving its thread safety.
Technologies: Android, Java, Bluetooth LE, Java Concurrency, Concurrent Programming, Mobile, VCS

Android Developer

2020 - 2021
  • Created an app that allows technicians to find a car's model from the catalog or its license plate and then order parts for it.
  • Supervised the work of an intern developer who covered the project with tests and added some new functionality.
  • Integrated the Phrase service to maintain the app's translation into more than 10 languages.
  • Created an app for Zebra tablet that is able to scan products' barcodes and make an order via the shop's API.
Technologies: Kotlin, Android, Model View ViewModel (MVVM), Coroutines, SVG, Android Material Design, Zebra Programming Language (ZPL), Barcode Reader, Phrase, Trello, Mobile Development, REST APIs, Mobile, VCS

Android Developer

2019 - 2021
  • Developed an app in Kotlin from the ground up that changes the client's DNS address and demonstrates the data compression capabilities of the company's service by playing YouTube videos.
  • Maintained an SDK for making apps that connect to the company's VPN.
  • Maintained documentation for the above-mentioned SDK's API.
  • Refactored the source code for an app that helps to reduce users' mobile traffic.
  • Debugged and added new functionality for different flavors (brandings) of the company's Android app for connecting to their VPN based on network conditions—mobile data, secure and insecure WiFi.
  • Updated the apps' target API level to meet the requirements of Google Play.
Technologies: Android, Java, Kotlin, VPN, Git, Phabricator, Robospice, Debugging, Flavors, Gradle, WorkManager API, EventBus, Model View ViewModel (MVVM), Widgets, Mobile Development, Mobile, VCS

Android Developer

2019 - 2020
Starlink Pharma SAS (via Toptal)
  • Added a few features (including barcode scanning functionality) to an existing Android app.
Technologies: Java, Kotlin, Android, Mobile Development, Mobile, VCS

Kotlin Android Developer

2018 - 2019
  • Added new features to two existing Android apps.
  • Incorporated Jetpack libraries into project.
  • Integrated dependency injection framework (Dagger2).
  • Helped to migrate from Realm to RoomDB.
Technologies: RxJava, RoomDB, Model View ViewModel (MVVM), GraphQL, Kotlin, Android, Mobile Development, Mobile, VCS

Freelance Android Developer with Strong Cryptography Experience

2018 - 2018
NDA Client (via Toptal)
  • Implemented an Android app from the groundup to deal with Ethereum transactions.
Technologies: AES, QR Codes, Cryptocurrency, Ethereum, Web3.js, Kotlin, Android, Mobile Development, Mobile, VCS

Freelance Android Developer

2018 - 2018
Rehash, LLC (via Toptal)
  • Created custom Android component (Draft.js editor) for React Native.
  • Fixed bugs in a React Native app.
Technologies: Draft.js, Android, JavaScript, Kotlin, Java, React Native, Mobile Development, Mobile, VCS

Freelance Mobile App Developer

2018 - 2018
POMCO (via Toptal)
  • Refactored an Android app.
  • Updated the UI and added animations.
  • Improved reliability of the Bluetooth connection.
  • Added support for the newest Android versions.
Technologies: Bluetooth, Android Data Binding, Android, Java, Mobile Development, Mobile, VCS, Google Maps

Freelance Android Developer

2018 - 2018
Codecacao (via Toptal)
  • Enhanced and supported the existing Android app.
Technologies: Android, Kotlin, Mobile Development, Mobile, VCS

Android Developer

2017 - 2018
  • Supported an Android messenger app.
  • Fixed chat latency and connection reliability issues.
Technologies: Mongoose, XMPP, Java, Android, Mobile Development, Mobile, VCS

Android Developer

2017 - 2017
UP Project Developments
  • Developed a voice recorder from scratch.
  • Built a simple Material Design UI.
  • Facilitated the auto sending of recorded files via SMTP.
Technologies: SMTP, Audio Recording, Java 8, Rx, Reactive Programming, Android, Mobile Development, Mobile, VCS

Freelance JavaScript Expert

2017 - 2017
MICA (via Toptal)
  • Supported user scripts for automating work with Google Spreadsheets.
  • Added new features using GAS.
Technologies: Spreadsheets, Google Apps Script, JavaScript, Google Sheets, VCS

Android Developer

2017 - 2017
Confidential Company
  • Supported an Android client app with embedded photo taking and recognition.
Technologies: Model View Presenter (MVP), DBFlow, Retrofit, Android Camera App, RxJava 2, Android Data Binding, Android, Mobile Development, Mobile, VCS, Google Maps

Freelance Android Developer

2016 - 2017
BioMetrix (via Toptal)
  • Created an Android app (from scratch) that communicated with peripheral devices via Bluetooth.
  • Contributed to the creation of the UX and design for the app.
  • Implemented a time-synchronization protocol with a 10-millisecond precision.
  • Implemented BT communication data recovery logic.
Technologies: Animated GIFs, Amazon Web Services (AWS), Retrofit, Bluetooth, Android, Mobile Development, Mobile, VCS

Android Developer

2016 - 2016
  • Supported an Android app that shows funny animated reminders about missed calls, events, emails, IMs, and more.
Technologies: Accessibility, Android, Mobile Development, Mobile, VCS

Android Developer

2016 - 2016
  • Created an Android mobile client application for a playlist management web-service.
  • Implemented a custom design.
Technologies: Realm, Audio Streaming, Android, Mobile Development, Mobile, VCS

Freelance Android Developper

2016 - 2016
Uprise (via Toptal)
  • Created an Android app for data visualization from scratch.
  • Used a chart graphical library to display data from weather stations.
Technologies: Android, Java, Mobile Development, Mobile, VCS

Freelance Android Developer

2016 - 2016
MCProHosting (via Toptal)
  • Fixed bugs and added a new functionality to an Android client for viewing live streams.
  • Added RTMP video-streaming support.
  • Changed the existing UI to make it compliant with the material design.
  • Helped to integrate the app with Google Cast.
Technologies: Real-time Messaging Protocol (RTMP), HTTP Live Streaming (HLS), Video Streaming, WebSockets, Android, Java, Mobile Development, Mobile, VCS

Android Java Developer

2015 - 2015
Jank Studios
  • Developed a social media app for Android.
  • Integrated Facebook, Twitter, and Instagram networks into the app.
Technologies: Instagram, Twitter, Facebook, JSON, REST, Java, Android, Mobile Development, Mobile, VCS

Android Java Developer

2015 - 2015
Raul Marco (Private Customer)
  • Created an app for picking assigned locations for your contacts on your Android device.
Technologies: SQLite, Java SE, Android, Mobile Development, Mobile, VCS

Android Java Developer

2015 - 2015
  • Added modifications to an existing open-source Android app to change its behavior.
  • Redesigned the brand for the above mentioned app.
Technologies: HTML Parsing, Java SE, Android, Mobile Development, Mobile, VCS

PhoneGap Developer

2015 - 2015
Yevhen Teneta (Private Customer)
  • Created a prototype of an animated audio-book reader app for Android and iOS using PhoneGap.
Technologies: CSS, JavaScript, HTML5, Cordova, PhoneGap, Mobile Development, Mobile, VCS

Java Developer

2012 - 2015
ELEKS Software
  • Developed a web app that manages cloud computers from AWS; this involved using J2EE/Spring stack for the back end and HTML/JavaScript/CSS for the front end.
  • Created a mobile app for contacting people inside a company using Scala for Android.
  • Supported an Android time-tracking app using Java and SQLite.
  • Built an Android market-type app using Java and implementing Material Design.
  • Maintained and tested PDF-rendering component of a web-service using Java.
  • Supported a Blackberry legacy time-tracking project using J2ME.
Technologies: Amazon Web Services (AWS), Mercurial, Scala, JPA, Bootstrap, jQuery, Ajax, CSS, JavaScript, HTML, EclipseLink, Spring, Java EE, ORMLite, SQLite, Java SE, Android, Mobile Development, Mobile, VCS

Java Mobile Developer | Lua Developer

2011 - 2012
  • Developed a smart-card emulator for Blackberry smartphones using Java ME.
  • Created a UI framework for TV applications with Lua script.
  • Built a testing framework using Lua.
  • Wrote unit tests for a framework running in an embedded system.
  • Developed the UI and business logic for a native Android app related to video processing.
  • Debugged and modified a Bouncy Castle library for working with cryptographic entities.
  • Created a video-player demo application with Lua scripting.
Technologies: Subversion (SVN), Lua, Android, PKCS, BlackBerry, Java ME, Java SE, Mobile Development, Mobile, VCS


The project is about auto-beautifying videos from your Android camera. It consists of a client and a server (pretty obvious). The server was developed on the customer’s side whereas we developed the Android client. No specific custom technologies were used, but we used many different parts of Android SDK (probably, the one we did not use was a database).


My client wanted me to improve the existing live-streaming Android app by fixing some bugs and adding new features.

The work included working with WebSockets, using 3rd-party library to view RTMP streams, adding a functionality that required an integration with new server APIs, and changing the app's UI to implement Material Design.

My client and end-users were satisfied with the app and the app's rating has increased since I worked on the project.


My client wanted an Android app to enable users to follow their favorite public figures on different social media networks in one place. So instead of switching back and forth between Facebook, Twitter, and Instagram you can have a mixed timeline of everything.

I implemented the app applying Material Design guidelines and the latest API guides suggestions. I integrated Facebook, Twitter, and Instagram APIs in a way that allowed me to manage them uniformly. The project required managing background tasks and using a SQLite database.

It was a really nice experience.

Contacts Location

A simple Android application that I was tasked to create for a client on another freelance platform. It lists the user's phone contacts and lets the user assign a location to any of them.


The target product was a kind of smart-card emulator. The idea is to use your mobile device as a security token (for example, to sign-in to Windows). Your device (BlackBerry, WinPhone, or Android) communicated with a so-called middle-layer via Bluetooth—exchanging some crypto-stuff such as keys, certificates, and more. The middle-layer in turn can be used by an end-user’s application to provide necessary security features.

My role was to develop the Blackberry client.

Android SDK for Creating Mesh Networks

An Android SDK for creating mesh networks via BLE. It enabled a device to send HTTP requests even if it was not currently connected to the internet directly. In such cases, the request would be forwarded via mesh to a device connected to the internet.

I was an Android developer on the project and implemented device disappearance propagation, internet connectivity detection, and propagation. I also stabilized the project by adding thread-safety and improving BLE communication synchronization.


RxJava 2, Retrofit 2, REST APIs, Android Universal Image Loader, AsyncTask, Google Gson, GSON, Android Support Library, LiveData, DBFlow, RxJava, MPAndroidChart, Butterknife, jQuery, Instagram API, Twitter API, Twitter SDK, Parse SDK, Facebook Open Graph API, Facebook SDK, SAX, Retrofit, AES, Apache HttpClient, Amazon API, Google Places API, Java Servlets, Quartz, Mobile HTML5, Google Maps, Google Maps SDK, OpenSSL, BouncyCastle, AtomPark SMS API, Android API, Web3.js, Robospice, WorkManager API


Android Studio, Google Sheets, Java Concurrency, Google Docs, Chrome Developer Tools, Eclipse IDE, Android Jetpack, Logging, Jira, Subversion (SVN), Notepad++, Git, 9-patch, Mercurial, Microsoft Word, TortoiseSVN, VirtualBox, GitHub, Spreadsheets, Mongoose, Amazon EBS, Apache Tomcat, Servlet, Javadoc, Adobe Photoshop, Amazon Simple Email Service (SES), Cron, FreeMarker, Microsoft Excel, Wireshark, VPN, Phabricator, Gradle, Trello


Rx, AndroidAnnotations, ORMLite, JUnit, PhoneGap, Dagger 2, Glide, Bootstrap, Draft.js, JPA, Spring JDBC, Spring MVC, Spring, Jakarta Server Pages (JSP), Turn.js, Media Players, PowerMock, Mockito, Android SDK, React Native


Java 8, XML, Java, Google Apps Script, GraphQL, Kotlin, HTML5, SQL, Pascal, Bash, HTML, JavaScript, Java SE, Delphi, Scala, Lua, CSS, XHTML, TypeScript, Flavors, Zebra Programming Language (ZPL)


RESTful Development, REST, Concurrent Programming, Generic Programming, Asynchronous Programming, Model View ViewModel (MVVM), Mobile Development, Functional Programming, Object-relational Mapping (ORM), Model View Controller (MVC), Unit Testing, Real-time Messaging Protocol (RTMP), Model View Presenter (MVP), Reactive Programming, Model View Intent (MVI), MVC Design, Testing, PKCS, Manual Testing, Agile Software Development, Scrum, Android Material Design


JSE, Android, Android Oreo, Firebase, Linux, Linux Mint, Mobile, Parse, Java ME, Eclipse, Twitter, Ethereum, Amazon Web Services (AWS), Windows XP, Windows, BlackBerry, Amazon EC2, Java EE, Bluetooth LE


Realm, SQLite, JSON, RoomDB, Relational Databases, Databases, MySQL, PostgreSQL

Industry Expertise



Android Data Binding, Debugging, Layout, EventBus, Memory Profiling, DOM, SMTP, Ajax, HTTPS, HTTP, Dom Manipulation, VCS, Google Material Design, Cordova, Android Animations, Apps, Writing & Editing, Mobile UX, Documentation, Encryption, Cryptography, Asymmetric Encryption, HTML Email, Email, HTML Parsing, Facebook, Instagram, HTTP Live Streaming (HLS), Accessibility, Animated GIFs, XMPP, Audio Recording, QR Codes, UI Animation, Audio Streaming, Android Camera App, Image Manipulation, MPch, EclipseLink, Video Capture, Video & Audio Processing, Video Editing, Videos, PDF, PDF Design, Checksum Calculation, Audio, Push Notifications, Digital Signatures, SSL Certificates, RSA, SSH, Bluetooth, DTD, RTMP, Video Streaming, WebSockets, SMS, Cryptocurrency, Cryptocurrency Payments, Coroutines, Widgets, SVG, Barcode Reader, Phrase, Mobile App Development

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