Senior UI Engineer

Location: Lisbon Workplace: Hybrid Build with us Since 2004, we've had one clear goal: to make payments and money management effortless for every business in Europe. Today, more than 250,000 companies use Mollie to get paid, manage money and grow – with products designed to be simple, scalable, and dependable. With 950+ Mollies across 14+ locations, we care deeply about autonomy and craft. So we work in small teams, with real ownership, and we trust you to make the right decisions. We're building for the long term, so we provide the tools you need, processes you can rely on, and a balanced work environment to help you do work you're proud of. Sound like your kind of place? Let's build together. Your impact The Merchant Experience domain's mission is to craft seamless experiences so every Mollie moment feels intuitive, secure, and supportive. The vision is simple: customers stay focused on growing their business while Mollie just works. We are hiring UI Engineers across the domain. We care deeply about quality and well-designed experiences, not only for our customers, but especially for the engineers building Mollie's products. This means creating clean, well-documented APIs, reliable tooling and smooth workflows that make development, testing, localisation, and releases easier and more predictable. It also means owning the design system and navigation experience that merchants interact with every day, driving engagement, accessibility, and product activation at scale. As a UI Engineer, you bridge the gap between platform capabilities and the teams that rely on them, working across the frontend, backend and infrastructure as needed. This is not a role where you ship one feature and move on. You will have real ownership, real visibility, and the chance to do work that matters at scale.   What you'll ship - Own and evolve the Mollie UI design system, ensuring consistency and quality across web and mobile. - Rebuild and improve the mobile navigation architecture, covering both the system design and the visual experience. - Improve app accessibility in line with compliance standards, making Mollie more inclusive for all merchants. - Strengthen testing practices and automation to raise reliability and reduce regressions across the app. - Own the Upsell infrastructure and in-app messaging that enables targeted campaigns to drive merchant engagement and product activation. What you'll bring - 5 or more years of experience developing mobile apps and web applications, with solid hands-on React and/or React Native experience and a genuine, deep understanding of JavaScript fundamentals at a low level. - Experience with CI/CD pipelines and app release processes. - Comfort working with native browser APIs and language primitives, and enough CSS confidence to implement interfaces using design system components. - A track record of building or maintaining products at medium to large scale, where code quality, reliability, and performance actually matter, including experience with test-driven development and REST API design. - A product-first mindset with end-to-end ownership, from design iteration through to delivery with a focus on user experience and measurable outcomes. - A generalist mindset with strong communication skill. - Always Be Shipping mindset: consistently delivering value to customers, where speed and quality go hand in hand. Grow your way At Mollie, growth is personal. We believe everyone should have the chance to develop their skills, explore new challenges and shape their career on their own terms. You'll get regular feedback and performance reviews to support your development, with fair and transparent salary reviews along the way. Many Mollies move into new roles or take on new projects to stretch themselves, and we actively hire from within to help you take the next step. No matter if you're aiming for promotion, exploring a different career path or building new skills, you'll be supported with the tools, trust and opportunities to grow your way. Unlock your full potential and join us to eliminate financial bureaucracy If you're excited by the idea of building what's next, for yourself and for thousands of businesses across Europe, we'd love to hear from you. Apply with your CV (in English) using the form below. Want a peek behind the scenes? Check out what life at Mollie is really like. AI at Mollie We believe in Always Be Shipping, and AI brings that philosophy to life across every team, every role, every day. AI is core to how we build. It helps us move faster, simplify work and make smarter decisions, creating real impact for the businesses we serve. We're looking for people who are excited to use AI to shape the future of finance with us.