Staff Machine Learning Engineer - LS Embedding

About the Team

The LS Embedding Team is at the forefront of building highly expressive, multi-entity embeddings that power Reddit’s recommendation systems. We go beyond standard two-tower architectures, leveraging Graph Neural Networks (GNNs), large-scale transformer models, and cutting-edge representation learning techniques to enhance personalization across Reddit’s ecosystem. Our work impacts content discovery, user engagement, and platform growth at a massive scale.

About the Role

As a Staff Machine Learning Engineer, you will own the technical direction for large-scale embedding models, guiding the development of state-of-the-art graph-based ML architectures and high-impact representation learning strategies. You will partner with leadership to define ML roadmaps, drive innovation in large-scale graph embeddings and deep learning techniques, and ensure scalable, efficient deployment of ML models in production. This role offers an opportunity to influence key AI-driven systems across Reddit while mentoring and uplifting the team’s technical capabilities.

Responsibilities

• Architect and lead the development of next-generation multi-entity embeddings, leveraging Graph Neural Networks (GNNs), transformers, and large-scale representation learning techniques.
• Define and execute the ML strategy for embedding models, identifying opportunities to enhance personalization and recommendation quality across Reddit.
• Lead research initiatives on scalable graph-based learning, self-supervised techniques, and real-time adaptation, bringing cutting-edge advancements into production.
• Partner with ML infrastructure teams to build high-performance, distributed training systems that efficiently scale across multiple GPUs and cloud environments.
• Establish and optimize real-time serving architectures for large-scale embeddings, ensuring low-latency inference and high throughput.
• Collaborate cross-functionally with teams in Feed Ranking, Ads, Content Understanding, and Core ML to integrate embeddings into Reddit’s key AI-driven systems.
• Mentor and guide senior and mid-level ML engineers, fostering a culture of excellence, innovation, and knowledge sharing.
• Stay at the forefront of AI research, evaluating and introducing new modeling paradigms to keep Reddit’s ML ecosystem at the cutting edge.
• Drive technical discussions, present findings to leadership, and contribute to long-term ML planning and decision-making.

Qualifications

• 8+ years of experience in machine learning engineering, with a strong focus on representation learning, large-scale embeddings, and recommendation systems.
• Expertise in Graph Neural Networks (GNNs), graph-based representation learning, and transformer architectures.
• Deep understanding of graph theory, knowledge graphs, and complex multi-entity relationships in machine learning applications.
• Proven ability to design, implement, and optimize scalable ML architectures, from distributed training to real-time inference.
• Hands-on experience with PyTorch Geometric (PyG), Deep Graph Library (DGL), TensorFlow, JAX, and large-scale ML model optimization.
• Strong software engineering skills in Python, C++, or similar languages, with experience in ML infrastructure, high-performance computing, and cloud-based ML pipelines.
• Demonstrated leadership in driving ML strategy, mentoring engineers, and influencing cross-functional teams.
• Experience with A/B testing, model evaluation frameworks, and real-time feedback loops in large-scale production systems.
• Excellent communication skills, with the ability to effectively present complex ML concepts to technical and non-technical stakeholders.

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