About Us About StackOne StackOne is the universal integration layer for modern SaaS products. We’ve raised $24m in 2 years, and we’re backed by top tier investors like Google Ventures and Workday Ventures. Our unified API platform lets vendors ship hundreds of native, white label integrations in days, not months, by abstracting away dozens of disparate third party APIs into a single, normalized interface. On top of those APIs, we provide AI Agent Actions so customers can build agentic workflows without wrangling OpenAPI specs. StackOne sits behind the scenes as an embedded iPaaS: SOC 2 compliant, multi-tenant, and invisible to end users powering integrations for future-of-work SaaS categories such as HR, Compliance, and AI Agents. Our customers are established B2B SaaS companies that: Sell to mid market and enterprise buyers Are building AI Agents in the near future Need deep, native integrations to win competitive deals and power their product Value time to integration over building connectors in house We typically close OEM and embedded licensing deals, multi-year (1 to 3 year) contracts, five to seven figure TCV, with a strong land and expand model. Key buyer personas are the CPO and CTO. 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. What success looks like after 12 months Design system adoption → 95 % of new UIs use shared components; visual regressions approach zero. Performance wins → Median Time to Interactive Developer velocity → Features squads ship UI changes 30 % faster thanks to reliable primitives and clear guidelines. Brand perception → qualitative feedback from users celebrates both functionality and “feel”, proving we are delivering exceptional user experience. 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.