- **5+ years of professional frontend engineering experience**, with at least 3 years building production React applications
- Deep expertise in **TypeScript**, **React 18**, and **Next.js 13/14** (App Router specifically)
- Strong CSS skills you understand the cascade, modern layout, and design-system thinking. Comfortable with Tailwind, CSS-in-JS, or CSS modules
- Experience building **complex, interactive data visualizations** graph layouts, time series, large tables using libraries like D3, visx, Recharts, react-flow, sigma.js, or similar (and knowing when to drop down to raw SVG/Canvas/WebGL)
- Performance engineering: you've profiled a slow React app, found the cause, and fixed it. Familiarity with React DevTools profiler, code-splitting, virtualization, memoization, and bundle analysis
- Accessibility: you've shipped a product that meets **WCAG 2.1 AA**, and you understand keyboard navigation, ARIA, screen-reader testing, and focus management as first-class concerns
- Comfortable working directly with backend engineers to shape API contracts (REST, streaming, WebSocket / SSE)
- Solid testing discipline unit (Jest / Vitest), component (React Testing Library), and end-to-end (Playwright or Cypress)
- Experience working in a startup or early-stage product comfortable with ambiguity, owns problems end-to-end, knows when to ship the 80% solution and when to invest in the 100%