SENIOR FRONTEND PERFORMANCE ENGINEER (EU) - REACT

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