Principal ML Engineer - Personalization & Matchmaking

Riot Games; Los Angeles (CA); On-site; USD 292,000 - 438,000; Full time

Benefits offered by this job

Medical, dental, and life insurance

401k with company match

Open PTO

Job summary

Riot Games seeks a Principal Machine Learning Engineer to define and drive the modeling architecture powering personalization, matchmaking, and social experiences across Riot’s player ecosystem. You will lead multi-model systems, develop skill inference and behavior models, and push fair, latency-aware AI across global scale.

Collaborate with Product, Data Engineering, and Software teams to shape data schemas, feature pipelines, and observability while mentoring senior engineers and advancing ML

Qualifications

• 10+ years in ML/Applied AI; 3+ years in principal/staff-level technical leadership.
• Experience with large-scale, real-time ML systems (recommendations, personalization, matchmaking).
• Expertise in graph ML, RL, and representation learning.
• Proficiency in PyTorch, TensorFlow, JAX, and modern data/serving tools (Ray, Kafka, Flink, Redis).
• Strong grounding in A/B testing, experiment design, and experience metrics.
• Track record of setting ML strategy and standards across teams.

Responsibilities

• Define and lead the modeling architecture for personalization, matchmaking, social graph recommendations, and player/community discovery.
• Architect multi-model systems combining skill, preference, trust, and safety signals for fair and meaningful matchmaking.
• Develop models for skill inference, player behavior prediction, trust & safety signals, and multi-objective optimization across fairness, latency, and experience quality.
• Build and optimize real-time inference systems for personalized content, store offers, matchmaking, and player interactions at global scale.
• Drive adoption of advanced modeling approaches including contextual bandits, reinforcement learning, graph ML, and session-aware personalization.
• Partner with Data Engineering and Product to shape data schemas, feature pipelines, telemetry standards, and model observability across the ML lifecycle.
• Define Responsible AI standards and implement fairness audits, bias mitigation, transparency, and safety mechanisms for matchmaking and social systems.
• Lead post-launch evaluations of algorithmic impact on player sentiment, community health, and ecosystem stability.
• Set organization-wide standards for model optimization (latency, throughput, memory), multi-model orchestration, and drift detection.
• Mentor senior ML engineers and data scientists, influencing system design, experimentation strategy, and modeling craft across organizations.
• Represent the ML discipline in cross-functional design reviews, driving alignment on technical decisions, data contracts, and long-term strategy

Skills

ML leadership

Real-time ML systems

Graph ML

Reinforcement learning

PyTorch

TensorFlow

JAX

Experiment design

A/B testing

Education

PhD preferred

Tools

Ray

Kafka

Flink

Redis

Job description

Riot Games seeks a Principal Machine Learning Engineer to define and drive the modeling architecture powering personalization, matchmaking, and social experiences across Riot’s player ecosystem. You will lead multi-model systems, develop skill inference and behavior models, and push fair, latency-aware AI across global scale.

Collaborate with Product, Data Engineering, and Software teams to shape data schemas, feature pipelines, and observability while mentoring senior engineers and advancing ML