Senior Machine Learning Engineer, AI Personalization

Role Description

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.

Qualifications

• 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.
• 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.

Benefits

• Remote work.
• Medical insurance.
• Flexible time off.
• Retirement savings plans.
• Modern family planning.