Senior JavaScript Engineer (React.js)

Intellias; Polska; On-site; PLN 180,000 - 270,000; Full time

Job summary

Intellias is seeking a Senior Frontend Engineer to own frontend features in a Next.js based application. You will collaborate with product, design, backend, and QA to drive technical decisions and deliver reliable features.

The role emphasizes building maintainable components, shared packages, and robust integrations with GraphQL and REST APIs. Strong CI/CD and code-review discipline are valued, along with proactive ownership of features.

Qualifications

• 5+ years of frontend development experience delivering production web applications.
• Strong experience with React, TypeScript, and modern Next.js (App Router, server/client rendering).
• Ability to design maintainable components and shared packages/APIs in a large monorepo.
• Experience integrating frontend with GraphQL and REST APIs, including generated types and evolving backend contracts.

Responsibilities

• Create technical vision and documentation.
• Participate in architecture and design efforts.
• Code review and optimization.
• Implement technical tasks, design and refactor code.
• Collaborate with other engineering teams to deliver high-quality software on time.

Skills

React

TypeScript

Next.js

Monorepo

Redux

AI tools

Tools

GitHub Copilot

Codex

Claude Code

Job description

Own the design and delivery of reliable frontend features across the Next.js application and shared packages. Collaborate closely with product, design, backend, and QA teams while helping the team make technical decisions.

Requirements

• Senior-level experience delivering production web applications, with 5+ years in frontend development.
• Strong experience with React, TypeScript, and modern Next.js, including App Router patterns and server/client rendering.
• Ability to design maintainable components and shared packages/APIs within a large monorepo.
• Experience integrating frontend applications with GraphQL and REST APIs, including generated types, loading and error states, and evolving backend contracts.
• Proficiency in responsive and accessible UI development using CSS Modules/SCSS, with the ability to work within an existing design system and follow design token conventions.
• Experience with frontend state management, such as Redux and React Context.
• Familiarity with monorepo tooling and CI quality gates, including linting, PR workflows, type checks, and builds.
• Strong debugging, code review, and written communication skills.
• Ability to take ownership of features through implementation, testing, release, and production follow-up.
• Experience using modern AI development tools to improve productivity, such as GitHub Copilot, Codex, or Claude Code.

Responsibilities

• Creating technical vision & documentation
• Participate in architecture and design efforts
• Code review, code optimization
• Technical tasks implementation, design, refactoring
• Collaborate with other engineering teams to resolve dependencies and deliver high-quality software on time, etc