Frontend Engineer (JavaScript, React & Native iOS Mobile), Senior

About Webellian

Webellian is a well-established Digital Transformation and IT consulting company committed to creating a positive impact for our clients. We strive to make a meaningful difference in diverse sectors such as insurance, banking, healthcare, retail, and manufacturing. Our passion for cutting-edge and disruptive technologies, as well as our shared values and strong principles, are what motivate us. We are a community of engineers and senior advisors who work with our clients across industries, playing a deep and meaningful role in accelerating and realizing their vision and strategy.

About the position

As a Senior Frontend Engineer within Advanced Analytics, you will lead the design and development of user-facing AI-enabled products across web and mobile platforms. You will own the frontend layer of production applications - building sophisticated React-based web interfaces and native iOS mobile experiences that bring AI capabilities directly to end users across the globe.

Key responsibilities:

• Architect and build production-grade React web applications: component design, state management, routing, performance optimization, and accessibility (WCAG compliance).

• Develop native iOS applications using Swift and SwiftUI (or UIKit where required), delivering high-quality, App Store-ready mobile experiences.

• Define and enforce frontend architecture standards: folder structure, component libraries, design system integration, and code quality conventions across web and mobile.

• Integrate frontend applications with REST APIs and event-driven backends, handling authentication flows, error boundaries, loading states, and real-time data patterns.

• Implement robust frontend testing strategies: unit tests (Jest, Vitest), component tests (React Testing Library), end-to-end tests (Playwright or Cypress), and iOS XCTest suites.

• Lead frontend performance engineering: bundle optimization, lazy loading, rendering strategies (SSR, CSR, ISR), Core Web Vitals, and iOS app performance profiling.

• Own the mobile development lifecycle on iOS: from Xcode project configuration and provisioning profiles to TestFlight distribution and App Store submission.

• Collaborate with UX Designers to translate designs into pixel-perfect, responsive, and accessible interfaces on both web and iOS.

• Champion AI-augmented development workflows using Claude Code: apply it actively for prototyping, code review, refactoring, and documentation generation.

• Conduct thorough code reviews, contribute to architectural decision records (ADRs), and mentor junior and mid-level frontend engineers.

• Work with DevOps to integrate frontend build and deployment into CI/CD pipelines: web app deployments, iOS build automation (Fastlane), and release management.

Required Experience & Skills

• 6+ years of professional frontend development experience, with a strong track record of shipping production applications at scale.

• Expert-level JavaScript and TypeScript: deep understanding of the language, async patterns, module systems, and type-safe application design.

• Expert-level React: hooks, context, state management (Redux Toolkit, Zustand, or equivalent), performance patterns, and large-scale component architecture.

• Strong native iOS development skills using Swift and SwiftUI; experience with UIKit is a plus.

• Solid experience with iOS-specific concerns: push notifications, background processing, Keychain, deep linking, and App Store review guidelines.

• Experience consuming and designing frontend integrations with REST APIs, including authentication (OAuth2, JWT), error handling, and data caching strategies.

• Strong CSS and layout skills: responsive design, CSS-in-JS (Styled Components, Emotion), or utility-first frameworks (Tailwind CSS).

• Experience with frontend build tooling: Vite, Webpack, or equivalent; understanding of bundling, tree-shaking, and deployment optimization.

• Hands-on proficiency with Claude Code: using it daily for development, debugging, refactoring, and documentation tasks.

• Proven ability to define architecture, set standards, and lead technical decisions in a senior individual contributor or tech lead capacity.

• Strong communication skills: able to collaborate effectively with designers, product managers, and backend engineers across global, distributed teams.

What we offer

• Contract under Polish law: B2B or Umowa o Pracę

• Benefits such as private medical care, group insurance, Multisport card

• English classes available

• Hybrid work (at least 1 day/week on-site) in Warsaw (Mokotów)

• Opportunity to work with excellent professionals

• High standards of work and focus on the quality of code

• New technologies in use

• Continuously learning and growth

• International team

• Pinball, PlayStation & much more (on-site)

Join a growing team of dedicated professionals! We love to pass on the knowledge to grow excellence, speak our minds without playing politics, and just enjoy hanging around together. If you share our passions - we want to meet you! So go ahead and apply