Senior Machine Learning Engineer, AI Personalization

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
Traditionally, ML systems were built to solve narrow tasks (e.g., item recommendations), with orchestration logic hard-coded outside the model. Increasingly, LLMs are becoming the orchestration layer, deciding which models to invoke, when to use them, how to interpret outputs, and how to chain steps together.
In this paradigm, the models we build deliver low-latency, large-scale personalization that advances Block's mission of economic empowerment. We work closely with Design, Product, and Engineering teams across Block's ecosystem, applying a spectrum of approaches from simple heuristics and embeddings to deep learning and large language models.
We also invest heavily in agentic engineering and AI-assisted tooling to enable high-velocity, reliable development. This includes code generation, automated testing, documentation, and developer workflows. You will play a key role in shaping how these practices scale, ensuring they remain rigorous, auditable, and trusted as their impact grows.
You Will

• Lead strategic initiatives in AI Personalization, driving the vision, architecture, and execution
• Develop and deploy new AI/ML models that power search & recommendations in traditional UX as well as new agentic interfaces
• Deploy to production at scale to personalize every user's experience
• Be a technical leader and establish quality practices that stick, make broader design decisions and set an example for others to follow
• Collaborate with a cross functional team of designers, business partners, and software engineers to build new technologies and features
• Design experiments, test them on production users, analyze and repeat

You Have

• 10+ years building and operating quality software
• Domain expertise in recommender systems, ranking systems, or similar with 5+ years of experience
• Led the development of complex models trained on large datasets powering customer facing features
• Strong software engineering skills
• Strong communication skills and customer empathy
• Experience with PyTorch, PySpark, Databricks and AWS is a plus

Technologies We Use and Teach

• We work with a modern, production-grade stack that includes industry-standard tools such as PyTorch, PySpark, Prefect, and Databricks
• Alongside these, a core part of the role is evaluating and prototyping with a rapidly evolving set of internal platforms and tooling
• Block is investing heavily in AI, and our modeling workflows are evolving accordingly
• This creates a rare opportunity to work with emerging systems as they take shape-both leveraging them in practice and influencing how they are designed
• The team is at the forefront of rethinking how models are built, validated, and deployed in an AI-first environment, with the goal of setting new industry standards

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 an equal opportunity employer evaluating all employees and job applicants without regard to identity or any legally protected class. We will consider qualified applicants with arrest or conviction records for employment in accordance with state and local laws and "fair chance" ordinances. We believe in being fair, and are committed to an inclusive interview experience, including providing reasonable accommodations to disabled applicants throughout the recruitment process. We encourage applicants to share any needed accommodations with their recruiter, who will treat these requests as confidentially as possible. Want to learn more about what we're doing to build a workplace that is fair and square? Check out our I+D page .
While there is no specific deadline to apply for this role, U.S. roles are typically open for an average of 55 days before being filled by a successful candidate. Please refer to the date listed at the top of this job page for when this role was first posted.
Block takes a market-based approach to pay, and pay may vary depending on your location. U.S. locations are categorized into one of four zones based on a cost of labor index for that geographic area. The successful candidate's starting pay will be determined based on job-related skills, experience, qualifications, work location, and market conditions. These ranges may be modified in the future.
To find a location's zone designation, please refer to this resource . If a location of interest is not listed, please speak with a recruiter for additional information.
Zone A:
$228,700 - $343,100 USD
Zone B:
$217,300 - $325,900 USD
Zone C:
$205,900 - $308,900 USD
Zone D:
$194,500 - $291,700 USD
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.