At a Glance
- Tasks: Craft pixel-perfect UIs and optimise performance for a cutting-edge SaaS platform.
- Company: Join StackOne, a fast-growing startup backed by top investors.
- Benefits: Enjoy meaningful share options, private health insurance, and a generous lunch budget.
- Other info: Hybrid work setup, annual team offsite, and a diverse, inclusive culture.
- Why this job: Be the first dedicated UX Engineer and shape the future of agentic integrations.
- Qualifications: 4+ years in front-end engineering with expertise in React and TypeScript.
The predicted salary is between 60000 - 80000 € per year.
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 interface. 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 focuses 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 performance 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?
- Meaningful share options (EMI) - share in the company's success as we grow.
- 25 days holiday + 1 additional day per year of tenure.
- Private health insurance - including dental & optical.
- £15/day lunch budget when working from our London office, up to £120/month.
- £1,000 for your home office set up + £500/year top-up.
- Annual team offsite to sunny spots (last ones were in Spain and Portugal).
- Join one of Europe’s fastest-growing startups.
- Work with a veteran team of ex-employees of Google, Microsoft, Oracle, Coinbase, JP Morgan and more.
- Health, fitness and gift card discounts.
- Cycle2Work and Electric Cars scheme.
- Hybrid work set up - typically 2 days in the office.
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.
Senior UI Engineer in London employer: StackOne
At StackOne, we pride ourselves on being an exceptional employer, offering a vibrant work culture that fosters innovation and collaboration. As a Senior UI Engineer, you'll enjoy meaningful share options, generous holiday allowances, and a hybrid work setup that promotes work-life balance. With opportunities for professional growth alongside a team of industry veterans, you'll be part of a fast-growing startup that values diversity and inclusivity while shaping the future of SaaS integrations.
StudySmarter Expert Advice🤫
We think this is how you could land Senior UI Engineer in London
✨Tip Number 1
Network like a pro! Reach out to folks in your industry on LinkedIn or at meetups. A friendly chat can open doors that a CV just can't.
✨Tip Number 2
Show off your skills! Create a portfolio showcasing your best UI projects. Make it easy for potential employers to see what you can do, especially with React and TypeScript.
✨Tip Number 3
Prepare for interviews by practising common questions and coding challenges. We all know the tech scene can be tough, so being ready will give you an edge.
✨Tip Number 4
Apply through our website! It’s the best way to get noticed. Plus, we love seeing candidates who are genuinely interested in joining our mission at StackOne.
We think you need these skills to ace Senior UI Engineer in London
Some tips for your application 🫡
Show Off Your Skills:Make sure to highlight your front-end engineering experience, especially with React and TypeScript. We want to see your portfolio showcasing those pixel-perfect UIs and any design systems you've built or contributed to.
Tailor Your Application:Don’t just send a generic application! Tailor your CV and cover letter to reflect how your skills align with our needs at StackOne. Mention specific projects where you’ve tackled performance tuning or built component libraries.
Be Authentic:Let your personality shine through in your application. We’re looking for someone who’s not just technically skilled but also passionate about creating great user experiences. Share your thoughts on design and performance!
Apply Through Our Website:We encourage you to apply directly through our website. It’s the best way for us to keep track of your application and ensure it gets the attention it deserves. Plus, we love seeing candidates take that extra step!
How to prepare for a job interview at StackOne
✨Know Your Stuff
Make sure you brush up on your React and TypeScript skills. Be ready to discuss your past projects in detail, especially those that showcase your attention to detail and performance tuning instincts. Having a portfolio that highlights your best work will definitely give you an edge.
✨Understand the Company
Familiarise yourself with StackOne's mission and products. Knowing how their AI Integration Gateway works and being able to articulate how your skills can contribute to their goals will show that you're genuinely interested in the role and the company.
✨Prepare for Technical Questions
Expect to dive into technical discussions about front-end engineering, performance metrics, and design systems. Brush up on your knowledge of Core Web Vitals and be prepared to discuss how you've tackled performance issues in the past.
✨Show Your Collaborative Spirit
Since this role involves working closely with designers and other teams, be ready to share examples of how you've successfully collaborated in the past. Highlight your ability to champion design quality and how you've contributed to creating a cohesive user experience.
