Senior Frontend Performance Engineer - React (Europe, Remote)

We're hiring Senior Frontend Performance Engineer to build one of the fastest web applications on the market — pushing frontend performance beyond what's possible with standard frameworks. The product is live and used by thousands of users; your job is to make it feel instant at any scale.

This is a high-ownership role where performance isn't a side quest — it's a primary business objective. You'll own it across the entire application.

What You'll Do

• Own frontend performance across the entire application — startup time, interaction latency, scrolling, rendering, memory, and perceived performance
• Design and implement advanced rendering, caching, preloading, and data synchronization systems
• Build custom performance infrastructure where existing libraries and frameworks fall short
• Profile and eliminate bottlenecks and UI jank using browser and application profiling tools
• Work with feature teams to ensure new functionality maintains performance standards
• Continuously benchmark the product against the fastest SaaS applications in the industry

What We're Looking For

Must have:

• 4+ years of frontend engineering experience, including 4+ years building large-scale React applications used by thousands of users
• Proven track record of significantly improving application performance in production
• Deep expertise in React, TypeScript, browser internals, rendering, memory management, and JavaScript performance
• Extensive experience with caching, virtualization, lazy loading, data synchronization, and state management
• Experience building custom infrastructure or frameworks — not just wiring up existing libraries
• Strong computer science fundamentals and algorithms; exceptional engineering standards and attention to detail
• Experience on products where performance was a primary business objective (think best-in-class SaaS speed, not "good enough")

Nice to have:

• Experience with WebAssembly, workers, or other advanced browser performance techniques
• Experience at a startup or fast-moving product company
• Contributions to performance tooling or open-source frameworks