Senior Machine Learning Engineer (Modeling), Risk

Since we opened our doors in 2009, the world of commerce has evolved immensely, and so has Square. After enabling anyone to take payments and never miss a sale, we saw sellers stymied by disparate, outmoded products and tools that wouldn't work together.

So we expanded into software and started building integrated, omnichannel solutions – to help sellers sell online, manage inventory, offer buy now, pay later functionality, book appointments, engage loyal buyers, and hire and pay staff. Across it all, we've embedded financial services tools at the point of sale, so merchants can access a business loan and manage their cash flow in one place. Afterpay furthers our goal to provide omnichannel tools that unlock meaningful value and growth, enabling sellers to capture the next generation shopper, increase order sizes, and compete at a larger scale.

Today, we are a partner to sellers of all sizes – large, enterprise-scale businesses with complex operations, sellers just starting, as well as merchants who began selling with Square and have grown larger over time. As our sellers grow, so do our solutions. There is a massive opportunity in front of us. We're building a significant, meaningful, and lasting business, and we are helping sellers worldwide do the same.

The Role

Square risk is a core function to ensure we keep the platform as well as merchants safe by gaining their trust and through our dedicated economic empowerment. This role sits in the Square Risk Machine Learning team and we partner with product, engineering, data science, policy and operations together to take a principled approach to manage fraudulent activities on our platform.

We leverage both traditional and SOTA AI and ML techniques to detect and mitigate risks in the ecosystem. We are looking for a strong machine learning engineer to build end to end AIML solutions to elevate our risk management and optimize the way we operate. If you are strong in AIML space, like to work with smart people around the world and have passion to continuously take ownership and pride to challenge and improve stuff, you are the right person we are looking for.

You Will

• Act as the ML modeling DRI, collaborating with platform engineers, product managers, data scientists, and policy analysts to drive the health and success of your risk squad.
• Become a risk domain expert and trusted technical leader in your risk squad.
• Build AI-powered automation tools or pipelines and propose improvements across Square's ML and broader Block risk ML org.
• Own the full lifecycle of ML solutions: data ingestion / processing / enrichment → model development → deployment → iteration.
• Champion reusable, scalable solutions by building tools, libraries, and packages that boost team velocity.
• Provide technical thought leadership and partner with peers and team lead to define roadmaps and execute on ambitious initiatives.
• Contribute positively to team culture as a collaborative, empathetic, and reliable teammate who uplifts others.

You Have

• 5+ years of software engineering or machine learning experience
• A degree (preferable graduate level) in Computer Science, Engineering, Statistics, Physics, Applied Math or a related technical field
• Hands-on experience independently designing and deploying ML solutions using methods such as tree-based models, deep learning, transfer learning, or reinforcement learning.
• Proficiency in modern ML stacks including: PySpark, PyTorch, MLflow, SageMaker, GCP Vertex AI, Workflow orchestration tools (i.e. Airflow, Prefect)
• Proficiency with containerization, orchestration, cloud platforms (AWS, GCP), and CI/CD practices.
• Experience collaborating with cross-functional teams to prioritize, scope, and deploy ML/AI solutions—both traditional and LLM-based—at scale.
• Strong written and verbal communication skills with the ability to explain complex concepts to technical and non-technical stakeholders.
• A natural sense of curiosity, and a passion for mentoring and helping shape a world-class machine learning team.

We're working to build a more inclusive economy where our customers have equal access to opportunity, and we strive to live by these same values in building our workplace. Block is a proud equal opportunity employer. We work hard to evaluate all employees and job applicants consistently, based solely on the core competencies required of the role at hand, and without regard to any legally protected class. We believe in being fai