Senior Machine Learning Engineer, Risk Modeling

Block builds technology to increase access to the global economy. Across our ecosystem including Square and Cash App we create tools that help businesses run and grow and individuals move manage and grow their money with confidence.

Square empowers sellers of all sizes with integrated omnichannel tools to accept payments manage operations access financial services and reach customers across online and in-person channels.

Cash App complements this by providing a fast accessible financial platform for millions of people to send spend save invest and borrow helping redefine how individuals interact with at massive scale across both ecosystems means trust and safety are foundational. Our teams build systems that protect real people and businesses safeguard financial activity and ensure our products remain reliable secure and easy to use.

Block is a global distributed company with a culture rooted in ownership creativity and impact. Whether supporting sellers on Square or customers on Cash App were united by a shared mission: to make the global economy more accessible and inclusive.

The Role

Were hiring Senior Machine Learning Engineers to join Blocks Risk Machine Learning organization where teams apply ML at massive scale to detect prevent and reduce fraud and abuse across Cash App and Square.

This opening supports multiple senior-level roles with team placement determined through a collaborative matching process based on your experience interests and current business needs. Today were growing teams focused on chargeback and fraud prevention as well as trust and safety initiatives supporting Cash App Families and teen banking.

Across teams your work will directly protect our ecosystem reduce financial loss and enable safe seamless financial experiences for millions of customers sellers and families.

Team Focus Areas

Depending on your background and interests you may join a team focused on one of the following areas:

Fraud & Chargeback Risk
Build machine learning models and systems that detect fraudulent transactions reduce chargebacks and protect the integrity of payments across Cash App and Square.

Trust Safety & Families
Develop machine learning systems that enable safe and trustworthy financial experiences for teens and families by detecting risky or abusive behavior strengthening account integrity and supporting long-term trust in Cash App.

Both teams value first-principles thinking rapid iteration and shipping production ML solutions with real-world impact.

You Will

• Partner with product engineering data science policy and operations to design and productionize ML-driven risk solutions at scale
• Own end-to-end machine learning systems from problem definition and modeling to deployment monitoring and iteration
• Lead technical decision-making within your workstreams and influence ML strategy and planning
• Build tooling and processes that improve the speed reliability and impact of the ML development lifecycle
• Apply state-of-the-art modeling techniques and third-party data sources to improve detection and decision-making
• Investigate emerging fraud abuse and risk patterns to proactively inform product safeguards and policy
• Collaborate closely with ML platform and engineering teams to ensure models operate reliably in real time and at scale

You Have

• 2 years of industry experience in machine learning applied AI or related fields
• Bachelors degree in a quantitative field (Computer Science Engineering Statistics Physics Applied Math); Masters or PhD preferred
• Proven experience independently designing deploying and maintaining ML solutions in production
• Strong familiarity with techniques such as tree-based models deep learning transfer learning or reinforcement learning
• Experience influencing technical direction and collaborating with cross-functional partners at scale
• Strong communication skills sound judgment and an ownership mindset
• Curiosity and alignment with Blocks mission of economic empowerment

Technologies We Use and Teach

• Python (NumPy Pandas scikit-learn XGBoost PyTorch TensorFlow/Keras)
• PySpark MLflow workflow orchestration tools (Airflow Prefect)
• GCP (Vertex AI) AWS
• Snowflake MySQL Tableau Mode
• Containerization CI/CD and production ML best practices

Required Experience:

Senior IC