Application Engineer I

About the role

Mollie is looking for an Application Engineer I to help build large‑scale, data‑driven systems that power our payments and money‑management platform across Europe. You will work on real‑time monitoring, predictive analytics, fraud screening and payment optimisation, collaborating with product, finance and engineering teams.

Key responsibilities

• Design and develop platforms for high‑volume transaction processing, including real‑time monitoring and predictive analytics.
• Build and operate ML/AI infrastructure for fraud detection, smart routing and automation.
• Develop cross‑domain features such as payment method ranking, dynamic 3D Secure, dunning, recovery and buyer intelligence.
• Design, maintain and evolve APIs and reusable services for internal and external consumers.
• Take ownership of technical initiatives from architecture through delivery while upholding engineering standards.
• Solve complex problems like anomaly detection and transforming transactional data into actionable insights.

Required profile

• 2+ years of experience building large‑scale applications.
• Strong “Always Be Shipping” mindset – delivering value quickly without sacrificing quality.
• Excellent communication skills and ability to work with diverse stakeholders.
• Creative problem‑solver with a product‑first approach.

Required skills

• PHP
• Java
• Go (or willingness to work with PHP/Java)
• C#
• Python

What we offer

• Opportunity to work on mission‑critical fintech systems.
• Collaborative environment with teams across Europe.
• Ownership of end‑to‑end features and technical initiatives.