Shape the design system behind a unicorn AI-native SaaS platform, scaling globally at speed.

Take the next step in your career now, scroll down to read the full role description and make your application. Why This Role? Stax is partnering with a unicorn AI-native SaaS scale-up that’s transforming how organisations use AI. Now they’re building a London engineering hub . Join as a UK founding engineer - hybrid working, high impact, and the chance to shape a category-defining platform from day one. The Opportunity This is a systems-level role at the intersection of design and engineering. You’ll be at the heart of a platform that’s changing how organisations use AI for customer support and product operations. In just four years, the team has: Pushed browser limits with D3-powered visualisations and real-time dashboards Open-sourced client-side analytics on DuckDB, bringing OLAP to the edge Built AI-native UIs that feel fast, intelligent, and fun Scaled a themeable design system adopted across multiple products and platforms Introduced micro-frontends that power independent, high-velocity teams—and let customers embed their own modules directly in the product Delivered deeply configurable UIs where layouts, components, and visualisations can be reshaped end-to-end via declarative config Your role: define the system that makes every pixel seamless, scalable, and lightning-fast. What You’ll Do Evolve the design system: tokens, theming, accessibility, visual language Build React + Web Component libraries for core + embedded apps Advance tooling: Storybook, Chromatic, Figma plugins Set standards and governance across design + engineering Deliver performant layouts and visualisations at scale Mentor peers on accessibility and performance-first development Tech Ecosystem You’ll Shape Design Tokens · Figma API · Storybook · React · Web Components · TypeScript · Tailwind CSS · Vite · NextJS · Jest · Cypress · Playwright What You Bring 8+ years in large-scale web apps, 2+ in design-system architecture Strong perspective on tokens, theming, multi-brand support Mastery of React + TypeScript, with library publishing experience Accessibility leadership (WCAG, ARIA, keyboard nav, colour contrast) Fluency in CSS methodologies and testing frameworks Excellent communication skills to align design, product, and engineering Bonus points for OSS contributions, Figma plugins, or micro-frontend orchestration Culture & Impact Speed with craftsmanship : fast feedback, continuous delivery, peer reviews Performance-first mindset : Core Web Vitals as product metrics Inclusive and global : teams across the US, Europe, and India Autonomy with accountability : design, guide, measure, iterate London hub : hybrid model, build the team and culture from the ground up Why join? Your design system will power products used by some of the world’s most ambitious teams. Join at a moment of hyper-growth and play a defining role in one of the most exciting SaaS platforms in the world. Stax welcomes applications from all backgrounds. Our client unfortunately can't offer visa sponsorship.