Efim is available for hire

Efim Goncharuk

Verified Expert in Engineering

Software Developer

Location

Prague, Czech Republic

Toptal Member Since

February 13, 2021

Efim is a UI lead software engineer with eight years of experience building multi-platform video streaming services, including video browsing, streaming, subscriptions, and payments. He has expertise in building web-based apps on the Next.js framework and six years of experience leading engineering teams. Efim is also well versed in security and communication protocols.

Single-page Applications (SPA)Front-end Web Development WebSockets REST APIs HTML5 Unit Testing JavaScript HaXe React CSS Git TypeScript Next.js Cryptography Formik Localization

Portfolio

DAZN

JavaScript, TypeScript, React, CSS, Jira, Over-the-top Content (OTT)...

Morgan and Morgan Arizona PLLC

HTML, CSS, React, TypeScript, CSS-in-JS, Jest, ESLint, Zustand, Localization...

Deltatre

JavaScript, TypeScript, HaXe, React, Sass, CSS, Git, Bamboo, HTML, Front-end...

Experience

HTML - 7 years JavaScript - 7 years HaXe - 7 years CSS - 7 years Git - 7 years React - 7 years TypeScript - 4 years Next.js - 3 years

Availability

Full-time

Preferred Environment

WebStorm, IntelliJ IDEA, Charles Proxy, Cryptography

The most amazing...

...thing I've developed is DAZN, a subscription-based video streaming service, which could be seen as Netflix for sports.

Work Experience

Senior Front-end Developer

2022 - 2023

DAZN

Created subscription tiering and account-sharing features for the DAZN app for multiple TV platforms.
Integrated pay-per-view subscription for Amazon Fire TV DAZN app.
Implemented PIN protection feature for DAZN app for multiple TV platforms.

Technologies: JavaScript, TypeScript, React, CSS, Jira, Over-the-top Content (OTT), Single-page Applications (SPA), Figma, REST, REST APIs, HTML5, Tizen, Visio, Web Development, Video APIs, HTTP Live Streaming (HLS), Streaming, Video Streaming, Unit Testing, Web Applications, Google TV, Fire TV, Video Players, Video Livestreaming

Front-end React and TypeScript Developer and Team Lead

2021 - 2022

Morgan and Morgan Arizona PLLC

Developed an app (Start.injury.com) that registers injury incidents with America's largest injury firm (TypeScript, React, Next.js, Emotion).
Developed an app (Injury.com) that manages and monitors client-registered injury claims.
Implemented complex advertisement screen animation (CSS and Emotion).
Implemented bespoke input elements UI library like text, password, date, editable drop-down, etc., which work smoothly on desktop and mobile devices and leverage native device capabilities.
Implemented end-to-end tests using Playwright and unit tests using Jest.
Implemented bespoke input validation solution inspired by Yup and Formik, which is small, simple, extendable, and with no external dependencies.
Implemented integrations with Google Tag Manager and Sentry.
Implemented A/B testing with Google Optimize on animated advertisement screens.

Technologies: HTML, CSS, React, TypeScript, CSS-in-JS, Jest, ESLint, Zustand, Localization, Sentry, Google Tag Manager, Emotion Library, Formik, Firebase, Playwright, Yup, Next.js, REST APIs, Chakra UI, WebStorm, MacOS, Slack, HTML DOM, APIs, Google Optimize, Single-page Applications (SPA), Figma, CI/CD Pipelines, HTML5, Startups, Web Development, Unit Testing, Web Applications, Node.js

UI Engineering Lead

2019 - 2021

Deltatre

Developed a subscription-based video streaming service, Telecine Play. The service offers a selection of its films, including the most recent titles. New titles are added to Telecine Play as soon as the day after their Telecine premiere.
Implemented the video playback UI and functionality.
Optimized the application deployment through AWS CloudFront content delivery network.
Performed code reviews in the Git source management environment.
Created tech tasks and tracked and fixed bugs using Jira as a task and bug tracker.
Configured continuous integration and continuous delivery (CI/CD) automation pipeline.

Technologies: JavaScript, TypeScript, HaXe, React, Sass, CSS, Git, Bamboo, HTML, Front-end, IntelliJ IDEA, Localization, REST APIs, WebStorm, MacOS, Slack, HTML DOM, APIs, Google Tag Manager, Sentry, Single-page Applications (SPA), Google Analytics, Figma, CI/CD Pipelines, HTML5, Over-the-top Content (OTT), Tizen, Visio, Web Development, Video APIs, HTTP Live Streaming (HLS), Streaming, Video Streaming, Unit Testing, Web Applications, Google TV, Fire TV, Video Players, Video Livestreaming

UI Engineering Lead

2015 - 2019

Massive Interactive

Developed a subscription-based video streaming service, DAZN. DAZN was launched in over 200 countries and territories worldwide.
Implemented core reach UI elements such as rails, tiles, forms, and pages, as well as UI performance optimizations, video playback UI, and functionality.
Integrated the app with many third-party payment systems, including payment options like credit cards, direct debit, Google payment, Amazon payment, and mobile operator payments. I also integrated the app with a fraud management system.
Implemented multiple partnership programs, gift codes, promotions, and voucher functionality. Integrated the app with analytics platforms like Google Analytics through Google Tag Manager and Conviva.
Performed implementation for web, Android, TVs, TV consoles, and bespoke platforms like X1 and SEMP TCL.
Conducted code reviews in the Git source management environment.
Led an engineering team of six people. Led Agile ceremonies, including stand-ups and grooming sessions.

Technologies: JavaScript, TypeScript, HaXe, React, RobotLegs, Redux, Sass, CSS, Git, Bamboo, Jira, Ant Design, Cordova, HTML, Front-end, Slack, IntelliJ IDEA, Node.js, WebSockets, Localization, REST APIs, WebStorm, MacOS, HTML DOM, APIs, Google Tag Manager, Sentry, Single-page Applications (SPA), Google Analytics, Webpack, Figma, CI/CD Pipelines, HTML5, Over-the-top Content (OTT), Tizen, Visio, Web Development, WebRTC, Video APIs, HTTP Live Streaming (HLS), Streaming, Video Streaming, Unit Testing, Web Applications, Google TV, Fire TV, Video Players, Video Livestreaming

Front-end Software Engineer

2014 - 2015

Banking Software Company

Developed a corporate internet banking system for the Česká Spořitelna Bank.
Designed a REST API for communication with server solutions.
Designed notification subsystem for the corporate internet banking system.
Tracked and fixed bugs using Jira as a reporting tool.

Technologies: JavaScript, Angular, Protractor, Git, Apiary API, HTML, Front-end, WebSockets, Socket.IO, REST APIs, WebStorm, HTML DOM, APIs, Single-page Applications (SPA), HTML5, Web Development, Unit Testing, Web Applications

Software Engineer

2007 - 2011

Sitronics

Developed rating and discounting services for mobile operators serving millions of subscribers.
Developed the online charging system for mobile operators serving millions of subscribers.
Created technical tasks and tracked and fixed bugs using TFS as a task and bug tracker.

Technologies: C#, LINQ, SQL, Entity Framework, Oracle, TFS, .NET, REST APIs, APIs, Unit Testing

Experience

DAZN App

http://www.dazn.com

DAZN is an over-the-top sports subscription-based video streaming service. It's a multi-platform app based on JavaScript, Cordova, and HaXe, available on most internet-connected devices, including smart TVs, smartphones, tablets, PCs, game consoles, streaming sticks, and set-top boxes.

I was a senior front-end engineer and, subsequently, the team lead. I created rich user interfaces and experiences in browsing video catalogs, watching video playback, creating subscriptions, and integrating with different payment systems.

Start.injury.com

http://start.injury.com

Register injury incidents with the US largest injury legal firm. A potential client goes through different (based on the injury type) simple question flows, answering in one click mostly. Advertisement animation screens are shown in between steps if needed.

App.injury.com

http://app.injury.com

A client of the US largest injury legal firm can review and manage registered injury incidents. The client signs the contract, provides required documents and detailed injury descriptions, monitors the progress, and communicates with a legal team.

Skills

Languages

JavaScript, TypeScript, HaXe, CSS, HTML, HTML5, Sass, Rust, C#, SQL

Frameworks

RobotLegs, Next.js, Redux, Ant Design, Angular, Protractor, Jest, .NET

Libraries/APIs

React, REST APIs, WebRTC, Emotion Library, Yup, Node.js, Apiary API, LINQ, Entity Framework, Formik, Playwright, D3.js, Three.js, Socket.IO

Tools

Git, WebStorm, Slack, Jira, Bitbucket, Sentry, Google Optimize, Bamboo, TFS, Google Analytics, Webpack, Figma, Visio, IntelliJ IDEA, Charles Proxy

Paradigms

HTML DOM, Unit Testing, REST

Other

Front-end, Single-page Applications (SPA), APIs, WebSockets, Web Development, Video APIs, Web Applications, ESLint, Zustand, Google Tag Manager, Cryptography, CI/CD Pipelines, Over-the-top Content (OTT), Startups, Video Streaming, Cordova, CSS-in-JS, Localization, Chakra UI, HTTP Live Streaming (HLS), Streaming, Fire TV, Video Players, Video Livestreaming

Platforms

MacOS, Oracle, Firebase, Tizen, Google TV

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