UI Engineer II: Scale Apps & Own Design System

UP42; Lisboa; On-site; EUR 60,000 - 90,000; Full time

Job summary

Mollie in Lisbon is seeking a UI Engineer to bridge frontend, backend and infrastructure, owning the design system and navigation experience used by merchants.

You will work across App Core and App Engagement, accelerating releases, building reusable patterns, improving accessibility, testing and automation, and driving product activation at scale.

This role offers impact across Europe in a hands-on, collaborative culture with a strong maker ethos.

Responsibilities

• Scale the mobile app architecture to support growing user demand.
• Improve and own the release process, moving from bi-weekly to weekly deployments.
• Build reusable patterns, tooling, and documentation for engineers across domains.
• Support debugging and feature delivery for teams across Mollie as a platform partner.
• Own and evolve the Mollie UI design system, ensuring consistency across web and mobile.
• Rebuild and improve the mobile navigation architecture, covering system design and visuals.
• Improve app accessibility in line with compliance standards.
• Strengthen testing practices and automation to raise reliability and reduce regressions.
• Own the Upsell infrastructure and in-app messaging for targeted campaigns.

Job description

Mollie in Lisbon is seeking a UI Engineer to bridge frontend, backend and infrastructure, owning the design system and navigation experience used by merchants.

You will work across App Core and App Engagement, accelerating releases, building reusable patterns, improving accessibility, testing and automation, and driving product activation at scale.

This role offers impact across Europe in a hands-on, collaborative culture with a strong maker ethos.