Sergii Vdovareize

Senior Frontend / Fullstack Engineer

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Summary

Over 16 years of experience as a software engineer, with a strong focus on frontend and product-oriented fullstack development. My background spans Consumer & AI Apps, EdTech, Programmatic Video Advertising, Telecom, and Wearables — from early fullstack work on web platforms and mobile apps to leading frontend teams at scale.

I've worked in small cross-functional teams where versatility is critical, as well as in large-scale enterprise environments with clearly defined roles and delivery pipelines. This experience has given me a solid understanding of architecture decisions, performance optimization, CI/CD, automated testing strategies, accessibility standards, analytics, and product growth mechanics.

I focus on building scalable, measurable, and maintainable systems — continuously looking for ways to improve performance, increase test coverage, automate workflows, enhance UX, and strengthen engineering culture.

Experience

Lead Software Engineer — Clario

Aug 2024 – Present Lviv

Crafts smart yet simple apps with a human touch, empowering better productivity, security, and lifestyles. The engineering focus is on building and scaling consumer-facing subscription products: optimising growth funnels, improving acquisition and retention, and shipping data-driven UX improvements across global markets.

Consumer-facing subscription products — growth funnels, retention, and data-driven UX at scale.

JavaScript, TypeScript, React, Next.js, Nest.js, Node.js, Playwright, Stripe
  • Building and optimizing sales funnels to increase conversion and customer lifetime value
  • Applying UX and behavioral design strategies to improve acquisition and retention
  • Setting up analytics and tracking systems for data-driven decision making
  • Designing automated visual regression testing workflows
  • Maintaining UI consistency and preventing production regressions
  • Optimizing sales funnels and UX for conversion growth
  • Analytics setup for data-driven decisions
  • Visual regression testing workflows

Senior Software Engineer — Beetroot

Mar 2020 – Jun 2024 Kharkiv / Lviv

Project: Inspera (Digital Assessment Platform)

Inspera. A cloud-based, end-to-end digital assessment platform used by universities, certification bodies, and professional organisations worldwide. It covers the full exam lifecycle — question authoring (25+ question types), secure exam delivery via a lockdown browser, AI-powered proctoring, collaborative grading, and analytics.

Inspera. Cloud-based digital assessment platform for universities and certification bodies — covering authoring, secure delivery, proctoring, and grading.

JavaScript, TypeScript, React, Node.js, Java, Mocha, Sinon, Enzyme, Puppeteer, Percy, TeamCity, SonarCube
  • Led development of major frontend features and platform improvements
  • Led a frontend team of 5 engineers and reduced onboarding time
  • Increased automated test coverage by 300%
  • Integrated visual regression testing, reducing visual bugs 3x
  • Implemented SVG theme automation to improve accessibility
  • Contributed to achieving WCAG 2.1 AA compliance
  • Added integration tests validating API integrity
  • Contributed to video and audio proctoring systems
  • Improved secure browser functionality
  • Strengthened long-term client retention through consistent platform improvements
  • Led frontend team of 5; cut onboarding time significantly
  • Increased test coverage 300%; integrated visual regression (3x fewer bugs)
  • WCAG 2.1 AA compliance, proctoring systems, secure browser
  • Contributed to video and audio proctoring systems
  • Led a frontend team of 5 engineers and reduced onboarding time

Senior Frontend Engineer — Team International

Sep 2018 – Feb 2020 Kharkiv

Client: Telenor Denmark

Telenor Denmark. One of Denmark's leading telecom operators serving 1.4M+ subscribers with mobile, broadband, and business connectivity. The main customer-facing product — Mit Telenor — is a self-service portal and app enabling subscription management, billing, data usage tracking, and personalised offers across both B2C and B2B segments.

Telenor Denmark. Leading Danish telecom (1.4M+ subscribers) — redesign of the Mit Telenor self-service portal and app.

JavaScript, React, Node.js, REST, Tealium, Adobe Analytics, TeamCity
  • Participated in full redesign of the main customer portal
  • Improved engagement and conversion metrics
  • Implemented and maintained Tealium Tag Management
  • Integrated Adobe Analytics tracking (marketing effectiveness +30%)
  • Built client-side reporting tools
  • Supported sales campaigns (+10% sales during campaign periods)
  • Conducted internal training sessions
  • Full portal redesign; improved engagement & conversion
  • Adobe Analytics integration (+30% marketing effectiveness)
  • Campaign support (+10% sales) and internal training
  • Built client-side reporting tools

Full Stack Software Engineer — Verizon Media

Apr 2016 – Jul 2018 Dublin

One by AOL. A legacy unified programmatic advertising platform, launched in 2015 by consolidating its ad tech assets — including Vidible (acquired 2014) and Adap.tv — into a single cross-channel stack covering video, display, and TV. The platform gave publishers and advertisers a self-serve marketplace for programmatic video at scale. Following Verizon's acquisition of Yahoo in 2017, AOL merged into Oath Inc., which rebranded as Verizon Media in 2019 and ultimately became part of Yahoo.

One by AOL. AOL's unified programmatic video & display ad platform — later rebranded through Oath to Verizon Media (now Yahoo).

JavaScript, Java, Node.js, MongoDB, Jasmine, Nightwatch, Jenkins, S3, Datadog
  • Developed high-performance HTML5 video player
  • Increased ad revenue through new provider integrations
  • Designed and maintained Player Version Manager (95% auto-update success rate)
  • Reduced production issues 10x via automated version control
  • Improved unit, UI, and mobile test coverage by 50%
  • Enhanced CI/CD processes
  • Refactored player into modular micro-components

Full Stack Software Engineer — Sigma Software Group

Dec 2014 – Apr 2016 Kharkiv

Vidible. A former independent cross-screen video management and ad exchange platform founded in 2012. It enabled publishers to distribute and monetize video content across sites and devices through a self-serve marketplace. AOL acquired Vidible in December 2014 (~$50M) and integrated it into One by AOL for Publishers, expanding AOL's programmatic video stack globally.

Vidible. Cross-screen video ad exchange acquired by AOL (~$50M, 2014) and integrated into One by AOL for Publishers.

JavaScript, Java, Ruby, Gradle, MongoDB, Jenkins, RSpec, JUnit
  • Extended and supported backend services
  • Enhanced video player functionality
  • Developed ad platform UI features
  • Introduced new video ad providers
  • Implemented player version switcher
  • Automated deployment flow (50% faster releases)

Software Engineer — Samsung Ukraine R&D Center

May 2013 – Dec 2014 Kharkiv

Tizen OS. A Linux-based, open-source OS developed by Samsung and the Linux Foundation as an alternative to Android — designed for wearables, mobile, and smart TVs, with HTML5 as the primary app development layer.

Tizen OS. Samsung's Linux-based OS for wearables and mobile, using HTML5 for app development.

Tizen OS, Tizen API, JavaScript, jQuery, Java, Android, Jenkins
  • Developed Tizen web-based reference applications
  • Built smart watch applications
  • Implemented smartphone–wearable interaction protocols
  • Worked on framework-level solutions for web apps
  • Optimized performance, memory usage, and battery consumption
  • Improved UI/UX for mobile and wearable environments

Full Stack Software Engineer — Sigma Software Group, Verizon Media

Dec 2014 – Jul 2018 Kharkiv, Dublin

Vidible / One by AOL. A unified programmatic video & display ad platform — later rebranded through Oath to Verizon Media (now Yahoo).

  • Developed high-performance HTML5 video player
  • Increased ad revenue through new provider integrations
  • Designed and maintained Player Version Manager (95% auto-update success rate)
  • Reduced production issues 10x via automated version control
  • Improved unit, UI, and mobile test coverage by 50%
  • Developed ad platform UI features
  • Automated deployment flow (50% faster releases)

Backend / Frontend Developer — Software Expert

Apr 2008 – May 2013 Kharkiv
PHP5, CodeIgniter, Symfony, JavaScript, MySQL, Selenium, WebOS, Blackberry
  • Implemented backend functionality for multiple web projects
  • Designed database architecture
  • Built reusable UI widgets (calendar, price calculator, rental forms)
  • Integrated OAuth, Google APIs, IMAP
  • Developed mobile applications (WebOS, Blackberry)
  • Implemented Selenium-based UI testing
  • Improved UX across multiple products
  • Backend, DB architecture, reusable UI widgets for multiple projects
  • OAuth/APIs integration; mobile apps; Selenium UI testing

Earlier Experience

Apr 2008 – Apr 2016 Kharkiv
  • Samsung Ukraine R&D — Tizen web apps, smart watch & wearable protocols, performance optimisation
  • Software Expert — Backend, DB architecture, reusable UI widgets, OAuth/APIs, mobile apps (WebOS, Blackberry)

Recent Pet Projects

  • Jar Tracker — Monobank jars donation dynamics tracker.
  • Snip — Download videos from social media.
  • Reactive Pages — Serverless number computations benchmark.

A web application for tracking balance changes and donation dynamics in Monobank public jars (fundraising campaigns). The backend uses a serverless and distributed architecture to poll, cache, and persist data at completely free tiers using NestJS, PostgreSQL, Prisma, Vercel, and Upstash Redis.

Try it

A lightweight web application that allows you to download videos from popular social media platforms quickly and easily. Built to download media with a single click from TikTok, Instagram, Twitter/X, YouTube, Facebook, and LinkedIn directly using an intuitive interface with clipboard integration.

Try it

A React web app that benchmarks serverless number computations across three major cloud providers (AWS Lambda, Google Cloud Functions, and Azure Functions). Visualizes response times and lambda execution times over asynchronous and synchronous load patterns, built with React 19, Chakra UI 3, and Framer Motion.

Try it

Bonus:
Stroop Effect Game

Thank you for reading through my entire CV. As a small token of my appreciation, I built a little brain teaser just for you!
Game rules: click the button that matches the ink color of the text, not what the word says.

Example: If you see RED you must click Green.
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