Senior Staff ML Engineer: User Understanding & GenAI

Reddit, Inc.; New York (NY); On-site; USD 266,000 - 372,000; Full time

Benefits offered by this job

Healthcare benefits

401k match

Global benefits programs

Family planning

Gender-affirming care

Mental health coaching

Flexible vacation

Parental leave

Job summary

Reddit, Inc. is seeking a Senior Staff Machine Learning Engineer to lead a next-generation user understanding initiative, building a unified, high-fidelity representation of users for personalization across the platform.

You will define the technical direction for embeddings, user profiles, and attribute modeling, and partner with product, infra, and downstream ML teams to deliver scalable, low-latency systems that impact Feeds, Search, Notifications, and Ads at global scale.

Qualifications

• You have at least 10 years experience building and scaling production-grade ML systems, particularly in user modeling, large-scale representation learning, or recommender systems.
• You have a track record of driving ambiguous, high-impact initiatives from concept to production, shaping both technical direction and execution.
• You are product- and impact-oriented: you care deeply about how your work moves real metrics (e.g., engagement, retention, revenue), not just model quality.
• You bring strong fundamentals in mainstream user understanding ML approaches (e.g., representation learning, behavioral modeling, user clustering), and understand their trade-offs in real-world systems.
• You are excited about the GenAI shift and have experience (or strong intuition) applying LLMs or foundation models to evolve existing systems, going beyond incremental improvements.
• You think in systems, not just models: you consider data, training, evaluation, serving, and adoption as a cohesive whole, and design with end-to-end impact in mind.
• You influence beyond your immediate team: partnering effectively with product, infra, and other ML teams, and driving alignment across multiple stakeholders.
• You raise the technical bar: mentoring senior engineers, leading design reviews, and establishing best practices for building reliable, scalable ML systems.
• You are comfortable navigating trade-offs across quality, latency, cost, and safety, especially in large-scale, user-facing systems.

Responsibilities

• Define a unified user understanding framework and strategy, including embeddings, attributes, and LLM-based profiles.
• Lead design and implementation of large-scale user models to improve personalization across Feeds, Notification, Search and Ads.
• Evolve user modeling with LLMs to build dynamic profiles and semantic reasoning over behavior.
• Design and build core components for embeddings storage, feature pipelines, and APIs with low latency and high availability.
• Drive experimentation and adoption with cross-team collaboration across Feeds, Notification, Search and Ads.
• Mentor senior engineers, lead design reviews, and enforce engineering best practices.

Skills

10+ years experience in production ML

User modeling

Representation learning

Recommender systems

Ambiguity-driven initiatives

Product impact orientation

GenAI / LLMs experience

Systems thinking across data, training

Mentoring senior engineers

Job description

Reddit, Inc. is seeking a Senior Staff Machine Learning Engineer to lead a next-generation user understanding initiative, building a unified, high-fidelity representation of users for personalization across the platform.

You will define the technical direction for embeddings, user profiles, and attribute modeling, and partner with product, infra, and downstream ML teams to deliver scalable, low-latency systems that impact Feeds, Search, Notifications, and Ads at global scale.