• You'll own the productionisation of our machine learning work end to end: real-time serving against SLAs, a standardised CI/CD path to production, GenAI and RAG system deployment, and the monitoring infrastructure that catches drift and quality degradation before business KPIs move. • You'll work on a GCP-native stack — Vertex AI, BigQuery, dbt, Airflow, and Terraform — on problems that matter from day one, with the autonomy to shape how the function scales and who joins it next. • You'll collaborate closely with Data Scientists, Platform, and Engineering, acting as both a technical owner and an advocate for Data Science needs across the organisation.

Role Description As a Senior ML / MLOps Engineer, you'll be a foundational hire in our new Data Science & Applied AI function — working in close partnership with our Data Scientists to take intelligent systems from prototype to production, and keep them performing once they're live. - Own the productionisation of our machine learning work end to end: - Real-time serving against SLAs - A standardised CI/CD path to production - GenAI and RAG system deployment - Monitoring infrastructure that catches drift and quality degradation before business KPIs move - Work on a GCP-native stack — Vertex AI, BigQuery, dbt, Airflow, and Terraform - Collaborate closely with Data Scientists, Platform, and Engineering - Act as both a technical owner and an advocate for Data Science needs across the organisation Qualifications - A track record of putting models into production alongside Data Scientists — classic ML, LLM/GenAI, or both - Deep understanding of the ML lifecycle from prototype to production, including real-time serving, feature stores, autoscaling, and blue/green deployments - Strong Python and SQL skills - Hands-on GCP experience, especially Vertex AI, Kubeflow pipelines, and BigQuery — or strong fluency on an equivalent cloud with a clear ability to get to Vertex fast - Solid CI/CD and production-monitoring experience, including model registries, versioning, drift detection, and automated retraining - Conversational-level English language skills Requirements - Experience with LLM evaluation, observability tooling, or RAG systems in production - Experience defining MLOps standards across multiple teams - Exposure to cost and latency management for GenAI systems Benefits - This is a fully remote position across the UK, Spain, and Poland. - Competitive salary plus bonus. - Private health cover, life insurance, pension, and enhanced parental leave — with specifics tailored to your location. - A generous holiday allowance plus public holidays. - Access to a global learning and development programme, wellbeing support, and discounts across partner platforms.

Role Description Guide research and engineering teams to close knowledge gaps and improve AI model performance in MLOps, training infrastructure, and ML framework-level topics. - Design challenging, domain-relevant tasks and write accurate, well-structured solutions to MLOps and ML systems problems. - Evaluate MLOps tasks and solutions and provide clear, written technical feedback. - Develop guidelines and detailed rubrics/evaluation frameworks to assess training pipeline design, distributed systems reasoning, and kernel-level optimization across tasks. - Collaborate with other subject matter experts to ensure consistency and accuracy in training data. Qualifications - 2+ years of dedicated professional experience in ML infrastructure, MLOps, or ML systems engineering at a recognized, top-tier organization. - Hands-on production experience with JAX at scale. - Experience writing or optimizing custom GPU kernels using Pallas or Triton. - Demonstrable career progression. - Ability to engage reliably for at least 40 hours/week during weekdays. - Strong written communication skills and the ability to explain complex technical decisions clearly. Company Description

Block builds simple, powerful tools that make progress towards an economy that's truly open to all. Each of our brands unlocks different aspects of the economy for more people. Square makes commerce and financial services accessible to sellers. Cash App is the easy way to spend, send, and store money. Afterpay is transforming the way customers manage their spending over time. TIDAL is a music platform that empowers artists to thrive as entrepreneurs. Bitkey is a simple self-custody wallet built for bitcoin. Proto is a suite of bitcoin mining products and services. Together, we're helping build a financial system that is open to everyone. Join us. The Role We're hiring Senior and Staff Machine Learning Engineers to join Block's 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, we're growing teams focused fraud & abuse prevention, merchant risk, credit underwriting (consumer & commercial lending), buy-now-pay-later decisioning, AI-powered customer support & conversational AI, agentic automation for investigations, and model risk governance. We'd love to hear from you whether your background is in adversarial ML, NLP/LLMs, credit modeling, or model validation. 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. 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 - 8+ years of industry experience in machine learning, applied AI, or related fields - Bachelor's degree in a quantitative field (Computer Science, Engineering, Statistics, Physics, Applied Math); Master's 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 Block's 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 Application Guidelines Candidates may submit up to 9 active applications within a 60-day period. Reapplications to the same role are accepted 90 days after a previous application has been reviewed. Use of AI in Our Hiring Process We may use automated AI tools to evaluate job applications for efficiency and consistency. These tools comply with local regulations, including bias audits, and we handle all personal data in accordance with state and local privacy laws. Contact us here with hiring practice or data usage questions. Every benefit we offer is designed with one goal: empowering you to do the best work of your career while building the life you want. Remote work, medical insurance, flexible time off, retirement savings plans, and modern family planning are just some of our offering. Check out our other benefits at Block. Block, Inc. (NYSE: XYZ) builds technology to increase access to the global economy. Each of our brands unlocks different aspects of the economy for more people. Square makes commerce and financial services accessible to sellers. Cash App is the easy way to spend, send, and store money. Afterpay is transforming the way customers manage their spending over time. TIDAL is a music platform that empowers artists to thrive as entrepreneurs. Bitkey is a simple self-custody wallet built for bitcoin. Proto is a suite of bitcoin mining products and services. Together, we're helping build a financial system that is open to everyone.