Senior Machine Learning Engineer, AI Personalization

Block

5h•Remote

About The Position

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. The role involves working with ML systems where LLMs are increasingly becoming the orchestration layer, deciding which models to invoke, how to interpret outputs, and how to chain steps together. The models built deliver low-latency, large-scale personalization to advance Block’s mission of economic empowerment. This position works closely with Design, Product, and Engineering teams across Block’s ecosystem, applying approaches from simple heuristics and embeddings to deep learning and large language models. The team also invests heavily in agentic engineering and AI-assisted tooling for high-velocity, reliable development, including code generation, automated testing, documentation, and developer workflows. The successful candidate will play a key role in shaping how these practices scale, ensuring they remain rigorous, auditable, and trusted.

Requirements

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

Nice To Haves

Experience with PyTorch, PySpark, Databricks and AWS

Responsibilities

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