Sergei is available for hire

Sergei Kurochkin

Verified Expert in Engineering

Front-end Engineer and Developer

Lisbon, Portugal

Toptal member since January 8, 2025

Expertise

React.js JavaScript CSS TypeScript Redux Jira GraphQL REST API Slack Development MacOS Visual Studio Development Next.js Node.js D3.js

Bio

Sergei is a senior front-end engineer experienced in React, TypeScript, and Next.js. He has contributed to Toptal's billing solutions, large retail company's employee portals, and low-code platforms. Skilled in performance optimization, data visualization, and team leadership, Sergei has enhanced web performance metrics, refactored monorepos, and developed scalable, high-performance solutions for startups and enterprises.

Portfolio

Toptal

React, GraphQL, Cypress, Jest, TypeScript, CSS

X5 Retail Group

React, TypeScript, JavaScript, React Query, Redux, D3.js, REST APIs, React Redux

Experience

React - 7 years
JavaScript - 7 years
Redux - 5 years
Jest - 5 years
Cypress - 5 years
TypeScript - 5 years
Next.js - 3 years
GraphQL - 3 years

Availability

Part-time

Preferred Environment

Slack, MacOS, Visual Studio Code (VS Code)

The most amazing...

...thing I've developed is a complex data visualization tool for internal analysts, leveraging big data analytics.

Work Experience

Senior Front-end Engineer

2022 - 2024

Toptal

Headed, planned, and coordinated multiple business initiatives that required thorough analysis, requirements gathering, and communication with design and product.
Delivered well-tested solutions on time and following the planned timeline.
Improved performance of billing pages by almost 80%. Managed to achieve desired values for LCP and LT (< 2s) by virtualization of content, JavaScript chunks optimization, and data loading optimization.
Planned and coordinated work on several large technical initiatives.

Technologies: React, GraphQL, Cypress, Jest, TypeScript, CSS

Senior Front-end Engineer

2019 - 2022

X5 Retail Group

Implemented efficient interfaces for internal analysts, featuring interactive canvases and large tables capable of displaying thousands of data entries.
Focused on optimizing solution performance by directing team efforts toward application profiling and efficient data and state management, given the substantial data volumes requiring display.
Led the coordination of efforts to refactor the internal UI kit to align with updated design specifications.
Developed flexible feedback gathering tool X5 forms that significantly sped up employee data gathering process.

Technologies: React, TypeScript, JavaScript, React Query, Redux, D3.js, REST APIs, React Redux

Experience

Domatest

A medtech startup that allows patients to take medical tests at home. It was a short-term project, and I led the web application development and acted as engineer manager.

At the start of the development process, I built a team of developers, system and business analysts, mobile app developers, back-end developers, and QA.

I integrated Agile project management practices into the workflow. In less than three months, my team and I determined, designed, and developed key features of MVPs and successfully launched web (CRM + website) and mobile apps.

Skills

Libraries/APIs

React, React Query, REST APIs, React Redux, Node.js, D3.js

Tools

Confluence, Jira, Webpack, Slack, Figma

Languages

JavaScript, TypeScript, GraphQL, CSS

Frameworks

Redux, Jest, Cypress, Next.js

Platforms

MacOS, Visual Studio Code (VS Code)

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