Senior Machine Learning Engineer

Hey there!👋

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, or insurers like N26, Trade Republic, flatexDEGIRO, Nationale Nederlanden, Qonto, Shine, Solarisbank, and more.

Having started our journey in January 2018 only, 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 developing best-in-class AI models alongside an exceptional and talented team. As a Senior Machine Learning Engineer in our Biometrics team, you will help us build the most reliable onboarding AI in the industry, with a focus on computer vision and multimodal user authentication.

You’ll work on complex and meaningful challenges—from concept to production—contributing directly to the accuracy, performance, and capabilities of our platform.

What You’ll Do

• Research, design, and develop deep learning models for classification and detection tasks using RGB, depth, video, and other data sources to detect user authenticity;
• Own the full lifecycle of machine learning projects—from data exploration and prototyping to model training, evaluation, deployment, and monitoring;
• Build robust prototypes and production-grade models using Python, TensorFlow, PyTorch, OpenCV, and other team-aligned tools;
• Write clean, maintainable, and testable code that adheres to the highest engineering standards;
• Rigorously validate experiments using our extensive in-house datasets and industry-standard metrics;
• Collaborate cross-functionally with our Platform, Fraud, and Mobile teams to ensure your models drive measurable impact across the product;
• Document your work thoroughly and review others’ code to foster a culture of quality and continuous improvement;
• Contribute to our culture of learning by participating in monthly knowledge-sharing sessions and staying up to date with the latest ML and CV research;
• Actively participate in technical decision-making, architectural design, and project scoping;
• Manage your tasks and priorities professionally and take full ownership of your deliverables.

Emphasis on Collaboration

At Fourthline, we foster a collaborative culture informed by industry knowledge (FinTech) and a deep understanding of our business objectives. As part of the team, you’ll engage in collaborative design sessions, reading groups, and continuous alignment with other teams and engineering disciplines.

Career Growth and Development

We offer opportunities for learning and development, allowing you to work alongside and learn from experienced engineers. As you grow within our team, there are possibilities to progress to Staff Engineer level and beyond—with clear pathways to further your technical, problem-solving, and communication competencies, as well as build your knowledge of the FinTech industry.

Job Requirements

Hard Requirements (Knock-Out Criteria)

• A completed MSc or PhD in Computer Science, Computer Vision, Machine Learning, Applied Mathematics, or a related field;
• 4+ years of software development experience with a strong focus on deep learning and computer vision;
• End-to-end experience deploying at least one deep learning solution into production;
• Strong proficiency in Python in production environments;
• Experience with at least one major deep learning framework (TensorFlow, PyTorch, JAX, or Keras);
• Solid understanding of deep learning fundamentals, including neural networks, CNNs, optimization, and loss functions;
• Proficient in evaluation methods (e.g. accuracy, precision, recall, ROC AUC);
• You hold EU citizenship or a valid Dutch work permit and are available to work on-site in Amsterdam at least 3 days per week (due to security requirements).

Nice to Have

• Industry experience in biometric authentication or KYC systems;
• Deep understanding of computer vision pipelines, especially with large-scale visual datasets;
• Understanding of mathematical concepts such as differentiation, approximation, function analysis, and linear algebra;
• Experience creating REST APIs, SDKs, or integrating ML models with microservices;
• Familiarity with software engineering best practices: testing, CI/CD, code reviews, observability, etc;
• Experience working with GPU-accelerated environments and ML Ops pipelines.

At Fourthline, we believe diversity enriches our culture and inspires you to do your best work. We value your unique talents and perspectives, welcoming them into a safe and inclusive working environment, to ultimately deliver the best products to our customers and society. You're welcome here. Fourthline is for everyone. 

Our hiring process is designed to be equal, fair, and transparent. We welcome people from all backgrounds, ethnicities, genders, sexual orientations, ages, abilities, religions, and experiences in life. If you're excited about this role, but your experience does not align perfectly with every qualification in the job description, we encourage you to apply anyways. You may just be the right candidate for this or other roles.