Senior Frontend Engineer

This role is best suited for a Senior Frontend Engineer with 4+ years of experience building complex React and TypeScript applications, particularly interactive and animation-heavy web products. The candidate should have strong expertise in SPA architecture, state management (ideally XState or similar), GraphQL, frontend testing, CSS-in-JS solutions, performance optimization, and modern build tooling, with bonus experience in canvas-based applications, graphics, or animation systems. They should be comfortable collaborating across teams, writing maintainable code, leveraging AI-assisted development workflows, and building highly polished user experiences at scale.

1. How would you architect a complex React SPA with large amounts of interactive state?
   I would separate UI state from business state, use a predictable state management approach such as XState or a similar solution, and design clear state transitions to keep the application maintainable as complexity grows.

2. What advantages do finite state machines provide in frontend applications?
   State machines make application behavior explicit, reduce edge-case bugs, improve predictability, and help manage complex workflows that would otherwise become difficult to maintain.

3. How would you optimize a React application containing complex animations and interactive graphics?
   I would minimize unnecessary renders, leverage GPU-accelerated animations, optimize rendering loops, and profile performance to ensure smooth interactions across different devices.

4. How does linear algebra apply to frontend graphics and animations?
   Linear algebra is fundamental for transformations such as translation, rotation, scaling, coordinate systems, vector calculations, and rendering interactive visual elements.

5. What challenges arise when building canvas-based applications compared to traditional DOM applications?
   Canvas applications require manual rendering, event handling, performance optimization, and state synchronization, whereas many of these concerns are handled automatically by the browser DOM.

6. How would you structure GraphQL data fetching in a React application?
   I would organize queries around feature boundaries, implement caching effectively, manage loading and error states consistently, and avoid over-fetching by requesting only the required data.

7. What are the benefits of using TypeScript in large frontend codebases?
   TypeScript improves maintainability, catches errors during development, enables safer refactoring, and provides better documentation through explicit types and interfaces.

8. How do you ensure frontend applications remain accessible while implementing advanced UI interactions?
   I ensure keyboard navigation, screen reader support, semantic markup, focus management, and accessibility testing are considered throughout the development process.

9. How would you evaluate AI-generated frontend code before merging it into production?
   I review it for correctness, performance, accessibility, security, maintainability, and alignment with project conventions, while validating behavior through testing and code review.

10. How do you balance pixel-perfect design implementation with engineering constraints?
    I collaborate closely with designers to understand priorities, maintain visual quality where it matters most, and make pragmatic tradeoffs that preserve both user experience and development velocity.

LottieFiles is hiring a Senior Frontend Engineer to help build the tools and experiences powering one of the world's leading animation platforms for designers and developers. In this fully remote role, you’ll create high-performance web applications using React, TypeScript, GraphQL, and modern state management solutions, working on complex interactive experiences that blend engineering, graphics, and user experience. You’ll collaborate across product, design, and engineering teams to deliver scalable, maintainable frontend systems while leveraging AI-native development workflows and modern testing practices. With flexible hours, unlimited leave, a generous learning budget, healthcare, and the opportunity to work on cutting-edge creator tools used globally, this is an exciting opportunity for frontend engineers passionate about design, animation, and exceptional product experiences.