Senior Software Engineer - Biometrics

At Fourthline, our mission is to fight financial crime. We help protect the global financial system by verifying millions of identities for banks, neobanks, online brokers, crypto exchanges, and insurers like N26, Trade Republic, flatexDEGIRO, Nationale Nederlanden, Qonto, Shine, Solarisbank, and more.

Having started our journey in January 2018, we're incredibly proud to count around 250 employees between our Amsterdam and Barcelona offices with over 50 nationalities.

Your Mission at Fourthline

Prevent financial crime by building best-in-class software alongside a talented and driven team, shaping our Biometrics solution at the core of Identity Verification, ensuring accuracy, scalability, and fraud prevention. You will work on complex, scalable, performant, data-intensive systems for facial recognition and liveness detection, and work closely with AI/ML engineers to integrate the latest models into production-grade services.

This role would be part of our Biometrics team, lead by Aytul Saka. Our Biometrics team builds and maintains backend systems that power identity verification through biometric technologies, and collaborates closely with AI/ML engineers to integrate cutting-edge models into production-grade services. Our core capabilities include face search, liveness detection, and deepfake detection, which are used as checks during the identity verification process. These services analyze user-provided data to ensure that a real, present person is being verified and to detect potential fraud or spoofing attempts.

As a Senior Backend Engineer at Fourthline, you will:

Design, develop, maintain, and improve our microservices, taking responsibility for thorough testing and reliable deployments.

Manage your tasks, priorities, and deliverables, taking joint ownership with your teammates for sprint goals.

Use your experience to contribute to our growth through lessons learned from your successes and failures.

Take responsibility for engineering excellence and participate in architectural decision-making within your team.

Contribute to thorough documentation to ensure clarity and long-term maintainability.

Understand the entire development lifecycle and work closely with other members in squads, including Platform and QA teams.

Apply both technical and interpersonal skills to solve challenges, recognizing that the best solutions often combine technology with people.

Collaboration

At Fourthline, we foster a collaborative culture informed by deep FinTech knowledge and a strong understanding of our business objectives. You will actively participate in chapter meetings, knowledge-sharing sessions, and cross-discipline collaboration with other teams and engineering disciplines.

Career Growth and Development

At Fourthline, we offer clear opportunities for learning and development, allowing you to work alongside and learn from experienced engineers. As you grow within our team, there are opportunities to grow your impact toward Staff Engineer level and beyond, including:

Deepening your technical expertise

Expanding your influence across teams

Strengthening your problem-solving and communication skills

Building your knowledge of the FinTech industry

Our Stack

.NET 8–10 — Our cloud-based microservices architecture includes REST APIs, Docker, Kubernetes, Message Queues (RabbitMQ), RDBMS (PostgreSQL), Wolverine, Marten (Doc + Event stores), and more.

What You Bring