Senior Machine Learning Engineer - Notifications Relevance

We’re looking for a Senior Machine Learning Engineer to join the Notifications Relevance team. Our goal: deliver the right content to the right user at the right time through push, email, and in-app notifications. This is a high-impact team driving DAU growth and long-term user retention by connecting users to what matters most to them.

Why this role?

• Tackle unique ML challenges at Reddit scale: recommend from hundreds of millions of posts, optimize across channels, and balance relevance, timeliness, and user fatigue.
• Build and productionize large-scale retrieval, ranking, and budgeting models that 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 closely with product, data science, and infra teams to drive measurable engagement outcomes (DAU, CTR, retention).

What you’ll do:

• 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.

Role 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.

Bonus points:

• 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.

Location: 

Reddit has a flexible first workforce. This role is 100% remote, and open only to candidates currently located within the United States. 

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

Reddit is proud to be an equal opportunity employer, and is committed to building a workforce representative of the diverse communities we serve.  Reddit is committed to providing reasonable accommodations for qualified individuals with disabilities and disabled veterans in our job application procedures. If, due to a disability, you need an accommodation during the interview process, please let your recruiter know.