Senior Machine Learning Engineer Notifications Relevance

Summary

Join Reddit's Notifications Relevance team as a Senior Machine Learning Engineer and contribute to delivering the right content to the right user at the right time. Tackle unique machine learning challenges at scale, building and productionizing large-scale models to personalize notifications for tens of millions of users. Work across the full stack, from designing deep learning models to scaling distributed training and inference pipelines. Collaborate with various teams to drive measurable engagement outcomes. Lead experimentation efforts, measure impact rigorously, and iterate quickly. Mentor other engineers and contribute to a collaborative ML culture.

Requirements

• 5+ years of industry experience (post-internship) working on large-scale machine learning systems
• Hands-on experience building, deploying, and scaling recommender systems (retrieval + ranking) in production
• Deep understanding of system-level trade-offs in large-scale recommendation pipelines (e.g. latency, throughput, storage of embeddings, feature freshness)
• Proficiency in Python; familiarity with frameworks like PyTorch or TensorFlow
• Experience with distributed training and inference using tools like Ray, PyTorch Distributed, or similar

Responsibilities

• Research, prototype, and productionize retrieval and ranking models that power personalized notifications at scale
• Design and build large-scale systems - from model pipelines to real-time serving - that handle Reddit’s massive user base and content volume
• Drive architecture decisions and roadmap priorities for the team’s ML systems
• Lead experimentation efforts, measure impact rigorously (offline + A/B), and iterate quickly
• Mentor other engineers and contribute to building a high-quality, collaborative ML culture

Preferred Qualifications

• Experience developing sequential modeling and real-time systems
• Familiarity with reinforcement learning or multi-objective optimization in recommendation systems
• Experience with orchestration tools (e.g. Airflow, Kubeflow), large-scale data processing (e.g., BigQuery, Dataflow)
• MS or PhD in Computer Science or a related field

Benefits

• Comprehensive Healthcare Benefits and Income Replacement Programs
• 401k Match
• Family Planning Support
• Gender-Affirming Care
• Mental Health & Coaching Benefits
• Flexible Vacation & Reddit Global Days off
• Generous paid Parental Leave
• Paid Volunteer time off