As the first dedicated UX Engineer, you will define the visual language and performance standards for an AI-powered integration platform. You’ll bridge the gap between design and engineering, owning the component library and micro-frontend architecture while ensuring every pixel and interaction meets the highest standards of craft and polish.
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Learn about Jack
Senior UI Engineer at StackOne
Join a high-growth London startup as their first dedicated UI/UX Engineer and shape the visual future of AI integrations. Backed by $24M from GV and Workday Ventures, this role offers the rare chance to own the design system and micro-frontend architecture for a platform used by top-tier SaaS companies. You’ll work alongside a veteran team from Google and Microsoft, blending high-end React craft with performance engineering. If you are obsessed with pixel-perfection, motion, and millisecond-level latency, this is your opportunity to set the standard for a category-defining product.
About this role
Role overview
About the company
StackOne
SoftwareCanterbury, United KingdomSeries A (VC-backed)
StackOne is the AI Integration Gateway for SaaS products and AI Agents. With operations in the UK and US, the company enables builders of SaaS platforms and AI Agents to orchestrate hundreds of scalable, accurate, and enterprise-grade integrations. Their platform combines 25,000 pre-mapped actions on 200 connectors, an AI-powered integration development toolkit, plus security by design: a real-time architecture, managed authentication and permissions, and end-to-end observability. The company was founded by a team of former Google, Oracle, JP Morgan, Coinbase, and Microsoft employees with a mission to build the most advanced integration infrastructure for generative AI applications. StackOne has experienced rapid growth, serving enterprise clients globally, and is backed by notable investors, including GV (Google Ventures), Workday Ventures, and Episode 1.
Backed by GV (Google Ventures), Workday Ventures, XTX Ventures, Episode 1 Ventures, Playfair Capital, Founders of GitHub, Founders of Onfido, Founders of Hofy, Angel investors from OpenAI, Angel investors from Google DeepMind, Angel investors from Microsoft, Angel investors from MuleSoft.
What you'll do
What you will do
- Lead the development and stewardship of a high-performance React component library and design system that powers all SaaS and AI agent integrations.
- Ship pixel-perfect user interfaces while optimizing Core Web Vitals, bundle sizes, and hydration patterns to ensure industry-leading performance.
- Build internal tooling and AI-assisted rules to empower other technical teams to contribute to the frontend while maintaining strict architectural standards.
Who you are
Who this is a fit for
- 4+ years of professional frontend experience with expertise in React, TypeScript, and modern CSS frameworks like Tailwind.
- Proven track record of building, migrating, or maintaining complex design systems and component libraries at scale.
- Deep technical knowledge of web performance tuning, including Lighthouse metrics, code-splitting, and monorepo tooling like NX or Turborepo.
Why this role
Why this role is remarkable
- Ownership of the entire UI ecosystem as the first dedicated UX specialist, setting the visual and technical bar for a product-led integration gateway.
- High-velocity environment backed by $24M from premier investors like GV and Workday Ventures, scaling rapidly to meet the demands of the agentic AI era.
- Exceptional engineering culture with a veteran team from Google, Microsoft, and Coinbase, offering generous perks like private healthcare and a dedicated home office budget.
Jack & Jill
How Jack & Jill work together
I get to know what you’re great at, then find roles you’d never find yourself.Ok, I'll go first. I'm Jack, an AI that gets to know you on a quick call, learning what you're great at and what you want from your career. Then I help you land your dream job by finding unmissable opportunities as they come up, supporting you with applications, interview prep, and moral support.
I recruit from Jack’s network and make the intro when I spot a great match.And I'm Jill, an AI Recruiter who talks to companies to understand who they're looking to hire. Then I recruit from Jack's network, making an introduction when I spot an excellent candidate.
Meet Jack
Jack gets to know what you're great at and what you want next, then searches 15 million jobs daily and helps you discover roles at companies like this.
How does this work?
Jack’s an AI agent for job searching and career coaching. He works for you.
Jill is the AI recruiter working for the company. She recruits from Jack’s network.
If it’s a match and the company wants to meet you, they’ll make the intro. In the meantime, if you’d like, Jack will send you excellent alternatives.