Sergiy Onenko, Full-stack Web Developer in Lviv, Lviv Oblast, Ukraine
Sergiy Onenko

Full-stack Web Developer in Lviv, Lviv Oblast, Ukraine

Member since April 16, 2019
Sergiy is a highly skilled senior full-stack developer who has worked at companies like NewMotion and Samsung. He has built his back-end skills at the largest charge network for electric cars in Europe. He created from scratch, the front end and partially the back end of a healthcare application. He regularly participates in startups and specializes in Angular, Ionic, and Express.js.
Sergiy is now available for hire


  • Toptal Projects
    Chrome, React, Amazon Web Services (AWS), Sketch, Figma, AWS, PostgreSQL...
  • NewFirePartners
    Node.js, Webpack, Angular, AngularJS, TypeScript, ECMAScript (ES6), JavaScript
  • Pubium
    Docker, React, Silhouette, Slick, PostgreSQL, MongoDB, Node.js...



Lviv, Lviv Oblast, Ukraine



Preferred Environment

Xcode, VS Code, IntelliJ, Git, Jira, Linux, OS X

The most amazing...

...experience was as the core developer at a successful startup for a healthcare application in the Netherlands.


  • Freelance Developer

    2019 - PRESENT
    Toptal Projects
    • Created functional design for cross-platform application "startup in stealth mode."
    • Configured AWS deployment process, EC2, Bash Script, PostgreSQL, and SSL.
    • Collected requirements for every next feature set, make demos, and standups.
    • Implemented the actual application, including authentication (Google, email), authorization, file upload, messaging, and user management.
    Technologies: Chrome, React, Amazon Web Services (AWS), Sketch, Figma, AWS, PostgreSQL, Node.js, Express.js, Ionic, Angular
  • Technical Lead/Architect

    2017 - 2019
    • Created architecture for plugin-based application from scratch with the ability to split the app (was not possible out of the box for Angular 5) into separate apps with no need to compile all together, meaning made apps independent for development but pluggable into one main application. It gave the ability to work independently for distributed teams.
    • Created a better development process, and introduced new build commands that allow simply to switch between development environment with no need to dig tons of documentation.
    • Greatly improved all team (30+devs) development speed by reducing application build time in development mode five times.
    • Created and contributed to the core library that used across all pluggable applications.
    • Shared knowledge to the team and distributed teams.
    Technologies: Node.js, Webpack, Angular, AngularJS, TypeScript, ECMAScript (ES6), JavaScript
  • Co-founder + Architect

    2017 - 2018
    • Designed and developed an application from scratch including delegation to other developers. Fully controlled step by step implementation, introducing Scrum process.
    • Created back end for management portal including roles system.
    • Designed and delegated front-end development of restaurants portal to other developers - allows to register restaurants, manage tables, days, and hours, and reservations.
    • Created the back end for Restaurants portal.
    • Created notifications application - for push notification across all existing infrastructure.
    • Set up all development and production environment including Docker and Swarm.
    • Integrated application with socials and mail services.
    • Coached and translated most important knowledge to team.
    Technologies: Docker, React, Silhouette, Slick, PostgreSQL, MongoDB, Node.js, Play Framework, Scala
  • Senior Web Developer

    2015 - 2016
    • Architected and developed the front end for web-based health-care applications from scratch. That alerts if microorganisms evolved resistance for certain antibiotics.
    • Designed and developed REST layer for application.
    • Added complex roles system.
    • Created Elasticsearch based aggregations and translated it to visualizations and tables.
    • Created complex filters system using tables and charts.
    • Contributed to Kibana; we needed additional features.
    Technologies: React, Gulp.js, AmCharts, AngularJS, ScalaTest, Elasticsearch, PostgreSQL, Akka Persistence, Akka HTTP, Akka Streams, Scala
  • Software Developer

    2012 - 2015
    • Designed and developed of RESTfull application that allows integrating partners to our services.
    • Contributed to the main web application - it allows users to manage their charge points, shows currently available charge points on the map, manages subscription plans, etc.
    • Contributed to core application that actually manages charging points behavior.
    • Contributed to the application that calculated payments charge point usage.
    Technologies: MySQL, Lift, Kendo UI, RabbitMQ, HAL, Akka, PostgreSQL, Slick, spray, CSS, SBT, AngularJS, Scala
  • Lead JavaScript Developer

    2011 - 2012
    Samsung R&D Ukraine
    • Designed and developed JavaScript/HTML5/CSS3 mobile UI library for RIA in e-Book Framework. The framework itself was integrated with C#.
    • Designed a web-based application for creating animation scenes.
    • Led team of seven developers.
    • Extended internal libraries for Tizen.
    • Supported Kies Air mobile app. Added more screen resolutions, more devices, and more abilities (e.g. preview photos).
    Technologies: NetBeans, Subversion (SVN), HTML5, CSS3, PHP, C++, JavaScript
  • Lead Web Developer

    2011 - 2011
    • Designed and developed a web-based internal application that allows managing team using regular reports from team members. Application is capable to: photo upload, data entry, generate web-based reports including charts, download PDF reports. Many different users used that app so I added complex roles system.
    • Made web base application for live streaming of conferences with pre-moderated chat with advanced roles system.
    • Created data analysis app that visualized requested data with advanced filtering and grouping.
    • Created landing pages for customers.
    Technologies: CSS, HTML, MySQL, PHP, MODx, Ext JS
  • Web Developer

    2010 - 2011
    • Created a custom website for a photographer with abilities to manage pictures and add watermarks to that.
    • Created web-based application for teachers, It allows to create courses, post articles, add tests, and attach videos.
    • Created a tool for students that allows to pass courses, pass exams, print course contents, and tests.
    • Made back end for vacation tracker.
    Technologies: CSS, HTML, MySQL, PHP, JavaScript, Ext JS



  • Languages

    CSS3, HTML5, JavaScript, TypeScript, Scala, SQL, Sass, Less, CSS, ECMAScript (ES6), Bash, C++, C, PHP
  • Frameworks

    Angular, JSON Web Tokens (JWT), Bootstrap, Express.js, Ionic, Play 2, AngularJS, Protractor, Apache Camel, Ionic 4, Ext JS, Play Framework, Akka, Kendo UI, Lift, Chrome
  • Libraries/APIs

    REST APIs, jQuery, React, Chart.js, Node.js, Google Charts API, Akka Streams, LeafletJS, Google Maps, RxJS, Slick, spray
  • Tools

    IntelliJ IDEA, Git, ScalaTest, Karma, Webpack, Jira, IntelliJ, VS Code, Xcode, Subversion (SVN), Figma, Sketch, Gulp.js, RabbitMQ, Bower, Canvas 2D, SBT, Kibana, Docker Swarm
  • Storage

    PostgreSQL, Elasticsearch, MySQL, MongoDB, Realm
  • Other

    Web Development, AmCharts, Data Visualization, Maps, Algorithms, Akka Actors, Akka Persistence, Integration Testing, Chrome Extensions, Safari Extensions, Architecture, Silhouette, HAL, Akka HTTP, AWS, Regression Testing, Machine Learning, Coaching, Leadership, OOP Designs, HL7, WebSockets, Domain-driven Design (DDD)
  • Paradigms

    Dependency Injection, Testing, Unit Testing, E2E Testing, Functional Programming, Scrum, Kanban, HL7 FHIR Standard
  • Platforms

    Godot, Visual Studio Code, OS X, Linux, NetBeans, MODx, Amazon Web Services (AWS), Arduino, Raspberry Pi, WatchOS, iOS, Docker, Meteor, DigitalOcean


  • Hacking with WatchOS 4
  • Complete Sketch 5 Course
  • The Complete iOS Bootcamp Development
  • Principles of Reactive Programming
  • Functional Programming Principles in Scala
    JUNE 2013 - PRESENT

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