Sergey is available for hire

Sergey Eremeev

Verified Expert in Engineering

JavaScript Developer

Bishkek, Chuy Province, Kyrgyzstan

Toptal member since June 7, 2019

Expertise

Web Development Debugging Front End Back-end Developers Full-stack SaaS Dashboard Integration MERN Stack Serverless Startup Development CTOs Agentic AI Chart.js Squarespace Development Google Maps Development

Bio

Sergey has more than a decade of experience in web and application development. He's worked with teams on projects that have shaped the industry, including large-scale eCommerce platforms serving giants like Walmart and small-scale web apps that helped secure contracts with companies like Calvin Klein. Sergey is not the type of developer to rest on his laurels, so he’s continuously perfecting his skills via learning, experimentation, and blogging.

Portfolio

Share a Refund LLC

PHP, Unit Testing, MySQL, Amazon Web Services (AWS), Zend Framework, Laminas...

Ziv Livnat

JavaScript, Python, Mapbox, Angular, QGIS, Web Development, API Integration...

Socol Pte Ltd

React Native, React, TypeScript, JavaScript, Next.js, Node.js, Prisma...

Experience

JavaScript - 15 years
React - 10 years
REST - 8 years
Node.js - 8 years
Vue - 7 years
Python - 6 years
Next.js - 6 years
React Native - 4 years

Work Experience

Full-stack Developer

2022 - 2023

Share a Refund LLC

Rebuilt the application from Zend to Laminas, modernizing controllers, services, models, APIs, reports, and background workers.
Replaced service-locator and circular-dependency patterns with explicit dependency injection, improving modularity, testability, and maintainability.
Migrated the front end from PHTML/AdminLTE to a responsive Vue 3, Vuetify, and Material Design 3 application.
Expanded UPS, FedEx, and DHL processing, including imports, rate calculations, reconciliation, and savings reporting.
Improved reliability through automated testing, API validation, data migrations, and background-worker optimization.
Contributed to Ask SARA, an AI-powered in-app assistant that helps users search the platform, navigate complex workflows, and understand features and business data through natural-language questions.

Technologies: PHP, Unit Testing, MySQL, Amazon Web Services (AWS), Zend Framework, Laminas, Object-oriented Programming (OOP), PostgreSQL, JavaScript, Vue, Artificial Intelligence (AI), Large Language Models (LLMs), Payments, Websites, Chatbots, AI Chatbots, Billing, Integration, Supabase, Debugging, Chrome DevTools, Web Standards, AI Agents, Multi-tenant SaaS, Distributed Systems, Prompt Engineering, Front-end Development, Front-end, Agentic Coding, Full-stack Development, Claude Code, LangChain, Web Application Architecture, AI Integration, Application Security, IT Security, Web Security, Observability, AI-assisted Development, Codex, Bug Fixes, Security, APIs, Software as a Service (SaaS), Data Privacy, Solution Architecture, System Architecture, CI/CD Pipelines, Agentic AI, Payment Gateways, OpenAI

Mapbox Vector Tiles Expert

2022 - 2022

Ziv Livnat

Developed a highly complex geocoding system for managing real estate properties on various scales.
Used the most up-to-date version of AngularJS to create a highly dynamic front-end application making the filtering and marking of different areas as user-friendly as possible.
Achieved a very high performance for large data containing hundreds of thousands of map tiles representing even the smallest areas.
Reached a very high level of customization for the app allowing the user to create their own tiles and presets on the fly, load saved data at a later point in time, and apply various visual filters to the points of interest.

Technologies: JavaScript, Python, Mapbox, Angular, QGIS, Web Development, API Integration, TypeScript, Full-stack, GitHub, Application Architecture, JSON, Functional Programming, HTML5, Object-oriented Programming (OOP), Websites, MVP Design, Front-end Development, Front-end, Full-stack Development, Bug Fixes, Startups, APIs, System Architecture

Head of Development | NFT Social Platform

2021 - 2022

Socol Pte Ltd

Led the team of developers to create a union of high complexity between social networks, eCommerce, and blockchain, resulting in a high-performing platform, allowing users to connect and achieve things that cannot be done on regular social networks.
Participated in assessing the work of developers, measuring their performance, and shaping the team to reach the best results in the shortest periods, saving funds for the client.
Took an essential part in designing the overall architecture, consisting of numerous APIs and SDKs for web and mobile (cross-platform) platforms.
Suggested and implemented key features, including databases, microservices, payment methods, performant back-end functions, and efficient payment algorithms.
Participated in daily stand-ups with developers, weekly reports to higher management, and occasional syncs with the marketing team to ensure the entire company was aware of the progress and the marketing team could perform as efficiently as possible.

Technologies: React Native, React, TypeScript, JavaScript, Next.js, Node.js, Prisma, Blockchain, Web3.js, Infura, MySQL, Amazon S3 (AWS S3), Figma, Ethers.js, PlanetScale, Tailwind CSS, NPM, Contentful, Back-end, AWS Lambda, Lambda Functions, Twilio, VoIP, Web Development, MongoDB, MERN Stack, Technical Leadership, Express.js, APIs, REST APIs, API Integration, Full-stack, CTO, Smart Contracts, GitHub, Architecture, Server-side Rendering (SSR), Application Architecture, Serverless, Software Architecture, iOS, Android, PostgreSQL, OAuth 2, JSON, SQLAlchemy, Terraform, DevOps, SQL, HTML5, Object-oriented Programming (OOP), Unit Testing, Stripe API, Stripe Payments, Stripe Checkout, Amazon Web Services (AWS), Amazon EC2, Payment APIs, Dashboards, Admin Panels, Payments, Websites, Search Engine Optimization (SEO), Billing, Integration, MVP Design, Debugging, Chrome DevTools, Web Standards, Front-end Development, Web Design, Front-end, Full-stack Development, Electron, FastAPI, Web Application Architecture, Application Security, IT Security, Cloudflare, Web Security, Headless Commerce, SvelteKit, Observability, Sentry, AI-assisted Development, Bug Fixes, Zustand, Team Leadership & Supervision, Compliance, Finance, Fintech, Startups, Security, Software as a Service (SaaS), Data Privacy, Solution Architecture, System Architecture, Firebase, Mobile App Security, Firebase Authentication, Leadership, WebSockets, CI/CD Pipelines, Docker, React Redux, React Router, Payment Gateways

Senior Full-stack Developer

2020 - 2021

Maintained the site and added various improvements to the industry-leading social network serving millions of users worldwide.
Developed and participated in the design phase of a feature visible to millions of users, which aimed to improve the safety of the end-users.
Took part in shaping the architecture of the new features developed over the 2020-2021 period for the consumer safety team.

Technologies: JavaScript, React, Python, GraphQL, Less, Jira, Agile, TypeScript, Back-end, Web Development, MongoDB, MERN Stack, APIs, REST APIs, API Integration, Full-stack, GitHub, Architecture, Application Architecture, Software Architecture, PostgreSQL, OAuth 2, JSON, SQLAlchemy, Functional Programming, Terraform, DevOps, SQL, HTML5, Object-oriented Programming (OOP), Unit Testing, Amazon Web Services (AWS), Amazon EC2, Dashboards, Admin Panels, Websites, Search Engine Optimization (SEO), Debugging, Chrome DevTools, Web Standards, Distributed Systems, Front-end Development, Front-end, Full-stack Development, FastAPI, Application Security, Web Security, Observability, Monorepos, Bug Fixes, Leadership, WebSockets, CI/CD Pipelines, Docker, React Redux, React Router

Full-stack Developer

2019 - 2019

Beautylish

Cleaned up a large portion of legacy code and rewritten the cart and checkout pages completely to utilize React and Redux.
Incorporated test-driven development into the development process.
Further expanded the testing side of the project to utilize both unit testing (Jest) and end-to-end testing (Cypress).
Participated in both front and back-end parts of the development process to shape the way the data comes from the back-end to ensure the best integration between all application parts.
Heavily participated in brainstorming and provided lots of useful ideas for the application to be more appealing to the end user.

Technologies: Git, HTML, Test-driven Development (TDD), Node.js, REST, CSS, Flask, Django, Python, Cypress, Jest, Redux, React, JavaScript, Back-end, Web Development, MERN Stack, Full-stack, GitHub, JSON, HTML5, Object-oriented Programming (OOP), Unit Testing, Payment APIs, Dashboards, Payments, Websites, Web Standards, Front-end Development, Web Design, Front-end, Full-stack Development, Headless Commerce, Bug Fixes, eCommerce, React Redux, React Router

Full-stack Developer

2018 - 2019

Agency,Mai?

Developed a process of optimizing 1GB+ files of complex map data to be displayed efficiently in the React web application.
Optimized multiple WordPress websites—scoring 95+ on Google PageSpeed.
Developed a custom translation mechanism for a Vue.js application—enabling the support of many languages.
Took part in developing a WordPress PHP framework for the simpler creation of custom website blocks.
Developed a plugin that scans a website for cookie usage and generates an easy-to-use cookie table and a front-end interface for a cookie bar and popup to make a website GDPR compliant.

Technologies: Git, jQuery, HTML, Node.js, REST, CSS, SCSS, WordPress, Webpack, Vue, React, PHP, JavaScript, Back-end, Ruby on Rails (RoR), Web Development, Squarespace, MongoDB, MERN Stack, Technical Leadership, Express.js, APIs, REST APIs, API Integration, Shopify API, Full-stack, GitHub, Architecture, Server-side Rendering (SSR), Application Architecture, Firebase, OAuth 2, JSON, DevOps, SQL, HTML5, Object-oriented Programming (OOP), Unit Testing, Zend Framework, Payment APIs, Dashboards, Admin Panels, Chart.js, Auth0, Laravel, Websites, Search Engine Optimization (SEO), Integration, Debugging, Chrome DevTools, Web Standards, Front-end Development, Web Design, Front-end, Full-stack Development, Web Security, Bug Fixes, Video Editing, Progressive Web Applications (PWAs), eCommerce, Solution Architecture, System Architecture, Leadership, Education Technology (Edtech), NestJS, CI/CD Pipelines, React Redux, React Router, WebRTC, Three.js, Payment Gateways

Front-end Developer

2014 - 2018

goTRG

Took part in developing a large-scale eCommerce solution which helped secure a contract with Walmart.
Developed a complex custom checkout solution with PHP and vanilla JavaScript.
Created a React application for an industry-changing car leasing platform.
Participated in the creation of a leading auto auction house application built with Meteor.
Developed a highly visual-rich application for a digital marketing agency built with vanilla JavaScript that utilizes custom-created JavaScript and CSS animations.

Technologies: Git, jQuery, HTML, CSS, Magento, WooCommerce, WordPress, React, Meteor, Gulp, Grunt, SCSS, JavaScript, Shopify, Web Development, Technical Leadership, Express.js, API Integration, Shopify API, GitHub, Serverless, JSON, SQL, HTML5, Object-oriented Programming (OOP), Zend Framework, Payment APIs, Dashboards, Admin Panels, Chart.js, Laravel, Websites, Shopify SEO, Search Engine Optimization (SEO), MVP Design, Debugging, Chrome DevTools, Web Standards, Front-end Development, Web Design, Front-end, Monorepos, Bug Fixes, Software as a Service (SaaS), eCommerce, CI/CD Pipelines, Docker

Project History

Gift Cards and Cart and Checkout Modules

https://www.beautylish.com/shop/gift-cards

Project:
I needed to build the cart and checkout pages and a gift card module for a large eCommerce business using React/Redux and following the best TDD practices.

Specifics:
• Existing checkout and cart pages were rewritten altogether, leaving the original design in place to align with the most modern web development practices using React/Redux.
• A large portion of code was cleaned up in order to provide the best re-usability together with improved site performance.
• Test-driven development was incorporated to achieve great code clarity for other developers working on the project (Jest and Cypress.io).
•We also needed the gift card module registration to be viewable.

Viking Cold Calculator

Project:
An energy savings calculator application (built with Vue.js) for a company that produces cooling solutions.

Specifics:
• This application utilizes multiple APIs—Pardot, Google Tag Manager, Gravity Forms API, Acton, CouchDB, and Chart.js—and functions as a progressive web app by allowing users to work with it offline. Gathered data is then sent to the server immediately as the device regains an internet connection.
• I developed this custom solution to simplify the entire application by simply editing a CSV file with the translated strings of text.
• The app functions equally well across all devices and through a kiosk app on tablet devices.

Resume Website

https://sergeyeremeev.com

I designed and built this interactive portfolio to showcase 15+ years of software engineering and technical leadership. Explore selected projects, the challenges behind them, and my contributions—from offline applications to complex commerce platforms. The site itself reflects my attention to typography, responsive design, accessibility, and subtle animation.

Automated Insights

Project:
A marketing website for the digital data processing agency which is full of visual animations and fancy transitions.

Specifics:
• It incorporates a custom-built alert system, which utilizes Google Maps geocoding to display alerts relevant to the user and complex mouseover effects to play videos forward and backward depending on the cursor position within the alert box.
• I developed custom pagination for the blog system, which allows one to add multiple blog sections to a page which will all be under the control of the browser history API—loading the content via Ajax for the smoothest user experience.
• The system allows the user to add data-to-text transforming animations easily to any title on the website and the ability to switch the entire look of the website via an option in the admin panel.

Hacker News Reader App

Project:
An app that fetches the most recent posts from the Hacker News platform.

Specifics:
• One thing that distinguishes this app from similar ones is that posts are displayed as soon as each one is fetched—not the whole bulk. This improves the interactivity of the app compared to similar solutions.
• Another feature of the app is that it works offline by utilizing the IndexedDB API.
• Custom filters at the top right and infinite scroll make this app a pleasure to use.

Frogger Game Clone

Project:
A famous game clone built with vanilla JavaScript using the best practices of object-oriented programming.

Specifics:
• I composed all of the code myself, covering all aspects of the application; this included requesting frames and ensuring that the app runs at 60 FPS to manage all objects' position, movement, and collisions.
• I further customized the initial concept to include difficulty levels defined by the obstacles, number of enemies, and their speed, as well as the ability to choose different characters and options to remove or reset obstacles with a single click of a button.
• The scoring system was introduced to add complexity to the application.

Twitter Bot

Project:
A PHP application that utilizes the Twitter API and displays formatted posts from a selected Twitter account in a selected visual.

Specifics:
• I set up a cron job on a server that executes the script that pulls tweets from a preselected account. It then formats the text from those tweets by removing images, emojis, links, and so on.
• The resulting text is then split into a certain amount of lines, and specific font size is applied for the message to occupy the container nicely. Finally, the text is plugged into an image containing the box for that text, and the result is published to the user's account.

Educated Body

Project:
A very design-centered website for an agency specializing in the gym and spa sector.

Specifics:
• Lazy loading was taken to the next level for this project to reach the smoothest user experience possible. Everything, including text, blocks, and images, appears in a certain way in a certain order to give this website a slick and structured feel.
• The existing plugins (a slick carousel) were customized to fit the client's needs to have the customized pagination behaving in a certain way. One section required two slick sliders to be tied together, resulting in complex logic and interactions which provide a very interesting user experience.
• A custom sticky sidebar on internal pages and very large font sizes were a challenge to overcome during the development of a responsive side of the website.
• I also added custom parallax effects to further enhance the visually pleasing nature of the website.

IntoUniversity

Project:
A React web application that was later rewritten with Vue.js for an organization providing local learning centers throughout the UK.

Specifics:
• The application is centered around a map created from a very complex set of data. Lower sets of data exceeded 1GB in size, so that data had to be optimized, simplified, split into logical chunks, and efficiently loaded so as not to impact load times too much.
• I used a React and React Router DOM for a smooth app feel, and all of the data is backed by a WordPress REST API (which I also developed from scratch to satisfy the client's needs).
• Later, the app was rewritten using Vue.js coupled with Vue router and Vuex for a better code organization following the best practices.

Room2

https://www.room2.com/

Project:
A marketing and booking website for a UK hotel business.

Specifics:
• Efficiently written scripts and CSS animations allow this app to be both visually pleasing and highly performant. The differences between mobile and desktop versions posed responsive challenges, which were gracefully overcome in the very early stages of development, thanks to strong communication among the design, management, and coding teams.
• A custom-written solution enabled a nice integration of the booking engine directly into the web page.

VipOutlet

Project:
A large-scale eCommerce project that helped sign a contract with Walmart.

Specifics:
• I built it with the Foundation CSS framework and PHP on top of the WordPress back end and the WooCommerce framework. The initial design has undergone many revisions that required careful planning for the website structure as well as CSS and JavaScript code, to make sure that this doesn't lead to a messy project.
• The checkout page is a completely custom solution that uses the best object-oriented practices and matches the complex requirements of the Walmart team.

Hulq Lease Calculator

Project:
A landing page and a React web application for an industry-changing car leasing platform in the USA.

Specifics:
• A landing page with a beautiful custom parallax effect for a maximum interactive experience for the user. A second version of the landing page was used for A/B testing via Google Tag Manager.
• A complex multi-step React application provides many ways for a user to find their dream car and make the leasing process as easy as possible for every client.

AutoAuctionMall

Project:
An auction house web application for finding great deals on cars; it was built using the Meteor framework.

Specifics:
• The application consists of a very complex filtering system that helps users find their car easier. It works well with multiple listing types such as buy-now, auction, reserved-price auction, etc.
• Multiple widgets, like a price calculator, were developed to guide users and help them make a much better decision.

Web3 Social Network Platform

This is a revolutionary social network platform built with Next.js and Ethereum blockchain. I took a CTO role to lead a team of highly skilled developers and architected a highly scalable system to serve millions of users.

From the technical side, I have chosen to utilize Prisma coupled with the PlanetScale cloud database and establish the link between the database, back end, and front end using tRPC for the absolute best type of safety and robustness of the application. We have utilized Vercel and AWS cloud service providers to have an entirely cloud-based platform, thus achieving the absolute best uptimes for the app.

Education

2010 - 2014

Bachelor's Degree in Civil Engineering

University of Bath - Bath, UK

Certifications

JULY 2016 - PRESENT

Front-end Web Developer Nanodegree

Udacity

Skills

Libraries/APIs

X (formerly Twitter) API, Flexbox, jQuery, Vue, Vue 2, React, Chart.js, React Router, Node.js, WordPress REST API, REST APIs, React Redux, Stripe, Stripe API, Stripe Connect, Shopify API, SQLAlchemy, Binance API, Three.js, Google Maps, Web3.js, WebRTC, Backbone.js, D3.js

Tools

Webpack, PostCSS, Gulp, Slack, PhpStorm, WebStorm, Git, JSS, Mongoose, Sequelize, Babel, Prisma, Figma, MetaMask, NPM, GitHub, Stripe Checkout, Claude Code, Sentry, Codex, Firebase Authentication, Mocha, NGINX, Terraform, Auth0, Grunt, Photoshop 7, Jira

Languages

PHP, GraphQL, Less, TypeScript, JavaScript, HTML, CSS, SCSS, Python, SQL, HTML5, PHP 5, Ruby

Frameworks

Vuetify, Redux, Jest, Cypress, Yarn, Svelte, Quasar, Next.js, React Native, Tailwind CSS, AngularJS, Draft.js, Express.js, OAuth 2, Zend Framework, Laravel, NestJS, Django, Nuxt.js, Knockout (Knockout.js), Ruby on Rails (RoR), Electron, Flask, Angular, tRPC

Paradigms

Functional Programming, Object-oriented Programming (OOP), REST, Agile, Test-driven Development (TDD), Jamstack, Application Architecture, Unit Testing, Web Application Architecture, DevOps, Search Engine Optimization (SEO)

Platforms

WordPress, Firebase, Mapbox, PlanetScale, Contentful, Shopify, AWS Lambda, Twilio, iOS, Android, Amazon Web Services (AWS), Amazon EC2, Visual Studio Code (VS Code), Docker, Linux Mint, WooCommerce, Linux, Blockchain, Google Cloud Platform (GCP), Magento, Meteor, Ethereum, Vercel

Storage

Databases, MongoDB, MySQL, PostgreSQL, JSON, Redis, Amazon S3 (AWS S3)

Industry Expertise

Web Design

Other

Web Development, CSS Grid, Styled-components, Front-end Development, Front-end Architecture, ESLint, WebSockets, Infura, Ethers.js, Slate, TinyMCE, Cryptocurrency Wallets, API Integration, Front-end, Back-end, Lambda Functions, VoIP, MERN Stack, Technical Leadership, APIs, Full-stack, CTO, Architecture, Server-side Rendering (SSR), Serverless, Stripe Payments, Payment APIs, Dashboards, Admin Panels, Payments, Websites, Billing, Integration, MVP Design, Debugging, Chrome DevTools, Web Standards, AI Agents, Multi-tenant SaaS, Distributed Systems, Prompt Engineering, Agentic Coding, Full-stack Development, AI Integration, Application Security, IT Security, Cloudflare, Web Security, Headless Commerce, SvelteKit, Observability, AI-assisted Development, Monorepos, Bug Fixes, Zustand, Team Leadership & Supervision, Startups, AI Architecture, AI Engineering, Progressive Web Applications (PWAs), Software as a Service (SaaS), Data Privacy, Communication, eCommerce, Solution Architecture, System Architecture, Leadership, Education Technology (Edtech), CI/CD Pipelines, Agentic AI, Payment Gateways, OpenAI, ParcelJS, OpenStreetMap, QGIS, Squarespace, Smart Contracts, Software Architecture, Laminas, Artificial Intelligence (AI), Shopify SEO, Chatbots, AI Chatbots, Supabase, FastAPI, LangChain, Video Editing, Bun, Compliance, Finance, Fintech, Security, Travel, Mobile App Security, Polygon, Middleware, IPFS, Non-fungible Tokens (NFT), FOMO, Large Language Models (LLMs)

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