Senior UX Engineer

About UsAbout StackOneStackOne is the universal integration layer for modern SaaS products. Weve raised $24m in 2 years and were 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 buyersAre building AI Agents in the near futureNeed deep native integrations to win competitive deals and power their productValue time to integration over building connectors in houseWe 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 existsStackOnes 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 theyre using the best-engineered platform on the market.What youll do80 % Front-end craft & design systems 20 % API-aware performance engineeringCollaborate 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 isnt.What youll bringMust-haves4 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-havesSvelte Web Components or other framework experimentation.Experience with auth flows (OAuth2 OpenID Connect) and secure front-end patterns.Web Motion & animation chopsPrior work on B2B developer tools or dashboards at seed-to-Series-B stage.What success looks like after 12 monthsDesign system adoption 95 % of new UIs use shared components; visual regressions approach zero.Performance wins Median Time to Interactive < 2 s on main dashboard;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 UsBe part of one of Europes fastest-growing startups making waves globallyCollaborate with a world-class team from Google Microsoft Oracle Coinbase JP Morgan and moreEquity participation through our employee stock option plan25 days PTO 1 additional day for each year of tenure (plus paid US holidays)Flexible hybrid work setupwork from home or join us in person when it suits you$1200 home office setup allowance $600 annual top-upHealth dental and vision insurance100% covered for employeesAccess to wellness fitness and lifestyle discountsAnnual company retreat in sunny destinations (past trips: Spain & Portugal)Ready to help us change the game for SaaS integrations Get in touch and lets 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.Required Experience:Senior IC Key Skills CSS,InVision,Balsamiq,HTML5,Information Architecture,Ux,Usability,Wireframing,UI,Axure,Responsive Web Design,Sketch Employment Type : Full-Time Department / Functional Area: Engineering Experience: years Vacancy: 1