Senior Staff Machine Learning Engineer, ML Understanding

1d•$266,000 - $372,400•Remote

About The Position

Reddit is seeking a Senior Staff Machine Learning Engineer to lead the user understanding initiative. This role involves building a unified, high-fidelity representation of each user to power personalization across the platform. The position requires deep expertise in ML user modeling approaches and the ability to leverage GenAI, LLMs, and foundation models for significant improvements. The engineer will set technical direction, lead the design and implementation of Reddit's core user representation layer, and ensure its scalability and reliability across various product areas. This is a high-impact role that will shape the user experience for millions of people by advancing personalization and relevance at a global scale.

Requirements

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

Responsibilities

Design User Understanding Strategy: Define a unified user understanding framework and strategy, including how users are represented (embeddings, tags, attributes, LLM-based user profile), computed, stored, and exposed. Provide thought leadership and set a long-term technical vision in user understanding and user modeling.
Build Foundational User Models: Lead the design and implementation of advanced user models, such as large-scale user representation learning (sequence-based, multi-interest, multi-task), to improve personalization across key Reddit products (Feeds, Notifications, Search, Ads) while balancing latency, cost, and performance.
Reimagine user understanding with LLM/Gen-AI: Evolve user modeling by leveraging LLMs to build richer user understanding, such as dynamic user profiles, intent inference, and semantic reasoning over user behavior. Explore how LLMs can augment or unify embeddings, attributes, and taxonomies for more adaptive, interpretable, and context-aware personalization.
Ship Large Scale User Understanding as a System: Partner with platform teams to design and build core components for large-scale learning and serving, including storage/retrieval for embeddings, feature pipelines, and APIs. Collaborate with ML/Ranking infra for low-latency serving, high availability, and integration with MLOps systems.
Drive Cross-Team Integration & Impact: Partner with Feeds, Notification, Search, and Ads teams to drive experimentation and adoption of new user understanding models with product teams across Reddit, ensuring measurable end-to-end impact on key metrics.
Set Technical Bar & Mentor: Mentor senior to staff engineers, lead design reviews, steward technical decisions across the user understanding domain, and champion and drive engineering processes and best practices.

Benefits

Comprehensive Healthcare Benefits and Income Replacement Programs
401k with Employer Match
Global Benefit programs that fit your lifestyle, from workspace to professional development to caregiving support
Family Planning Support
Gender-Affirming Care
Mental Health & Coaching Benefits
Flexible Vacation & Paid Volunteer Time Off
Generous Paid Parental Leave
Equity in the form of restricted stock units
Commission (depending on position offered)
Medical, dental, and vision insurance
Generous time off for vacation
Parental leave