Job Description

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

Why This Role?

Stax is partnering with a unicorn AI- SaaS scale-up that’s transforming how organisations use AI. Since 2020 they’ve:

• Grown rapidly to a global team
• Raised $100M+ in Series A funding
• Reached unicorn status with a $1.1B valuation

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- 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
• 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, 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.

Apply today or reach out directly to Stax to start the conversation.