UI Engineer II

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
Depending on which team you join, your work will focus on one of the following areas:

App Core

• Scale the mobile app architecture to support growing user demand, with a focus on quality and long-term maintainability.
• Accelerate the app release cadence by improving and owning the release process, moving from bi-weekly to weekly deployments.
• Build reusable patterns, tooling, and documentation that allow engineers across all domains to contribute to the mobile app without needing deep mobile expertise.
• Support debugging and feature delivery for teams across Mollie, acting as a platform partner to product teams who depend on the AppCore foundations.

App Engagement

• 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

• 4 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

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.

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.