About StackOne: StackOne is the AI Integration Gateway for SaaS products and AI Agents. Backed by GV and Workday Ventures ($24M raised), we help builders of SaaS platforms and AI Agents orchestrate hundreds of scalable, accurate, and enterprise-grade integrations. Our 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. Join us on our fast trajectory to build the future of agentic integrations. Why this role exists StackOne’s product experience is our brand. As our first dedicated UX Engineer you will be the in-house authority on taste, polish, and performance. You will own the component library, shape our micro-frontend architecture, and ensure that every pixel, motion, and millisecond of latency makes customers feel like they’re using the best-engineered platform on the market. What you’ll do 80 % Front-end craft & design systems 20 % API-aware performance engineering Collaborate with our Designer to define & steward our design system – set the visual language, build reusable primitives, and maintain libraries that power every StackOne user interfaces. Ship pixel-perfect UIs – React (primarily) plus; own theming, performance, and thoughtful motion. Make performance a feature – instrument Core Web Vitals, budget bundle sizes, optimise hydration patterns, and chase performance where it matters. Provide and maintain internal tooling as well as AI rules to allow every technical team to contribute to the front-end while aligning with the best practices you will help set. Prototype & validate – turn product ideas into interactive proofs-of-concept that help PMs and designers converge on the right solution fast. Champion taste & detail – host design-quality critiques, stamp out visual debt, and be the go-to voice when “good enough” isn’t. What you’ll bring Must-haves 4 yrs professional front-end engineering with a portfolio that focus on the details. React & TypeScript at production scale; comfortable with hooks, suspense, and server components. Deep CSS fluency (Tailwind or equivalent) and experience of modern browser APIs. Proven track record building or migrating component libraries/design systems. Strong performance tuning instincts: Lighthouse, Core Web Vitals, bundle analysis, code-splitting. Familiarity with monorepo tooling (NX or Turborepo) and micro-frontend patterns. Ability to dive into back-end code (Node, React-router, sveltekit) to remove perf bottlenecks, instrument metrics, or adjust API shape. Nice-to-haves Svelte, Web Components, or other framework experimentation. Experience with auth flows (OAuth2, OpenID Connect) and secure front-end patterns. Web Motion & animation chops Prior work on B2B developer tools or dashboards at seed-to-Series-B stage. Why Join Us? Be part of one of Europe’s fastest-growing startups making waves globally Collaborate with a world-class team from Google, Microsoft, Oracle, Coinbase, JP Morgan, and more Equity participation through our employee stock option plan 25 days PTO 1 additional day for each year of tenure (plus paid US holidays) Flexible hybrid work setup—work from home or join us in person when it suits you $1,200 home office setup allowance $600 annual top-up Health, dental, and vision insurance—100% covered for employees Access to wellness, fitness, and lifestyle discounts Annual company retreat in sunny destinations (past trips: Spain & Portugal) Ready to help us change the game for SaaS integrations? Get in touch and let's chat! We believe diversity drives innovation. We encourage individuals from all backgrounds to apply. As an equal-opportunity employer, we celebrate diversity and are committed to creating an inclusive environment for all employees.