Senior Principal Machine Learning Engineer (Central Product Insights)

Riot Games; Los Angeles (CA); On-site; USD 240,000 - 360,000; Full time

Benefits offered by this job

Healthcare

Life insurance

Paid time off

Retirement match

Play Fund

Donation matching

Job summary

Riot Games is seeking a Sr. Principal ML Engineer to define the modeling architecture powering personalization, matchmaking, and social features across the player ecosystem.

You will lead an AI and modeling layer with product, software, and data engineers to turn data into intelligent, fair experiences for players. You will collaborate on live-service ML pipelines, multi-model orchestration, and responsible AI standards, ensuring low latency and scalable inference for player interactions at

Qualifications

• 15+ years in Machine Learning or Applied AI, with 3+ years in principal or staff-level leadership.
• Deep expertise in graph ML, reinforcement learning, and representation learning.
• Proven experience in real-time, large-scale ML systems such as matchmaking, recommendations, or personalization.
• Strong track record in ML standards, A/B testing, and player experience metrics.
• Background in game development, player behavior modeling, or social ecosystems.
• Experience in trust & safety, toxicity detection, or community health models.
• Familiarity with Vertex AI and SageMaker or internal real-time inference platforms.
• Proven ability to integrate ML systems with live-service game backends.

Responsibilities

• Define and drive the modeling architecture powering personalization, matchmaking, and social experiences.
• Lead ML modeling layer with cross-functional teams to convert data into intelligent experiences.
• Build real-time inference systems for personalized content, offers, and player interactions at scale.
• Drive multi-objective optimization balancing fairness, latency, and quality of experience.
• Establish evaluation protocols for match quality, satisfaction, and toxicity mitigation.
• Mentor senior ML engineers and data scientists; guide system design and experimentation practices.

Skills

PyTorch

TensorFlow

JAX

Graph ML

Reinforcement learning

Representation learning

Real-time ML systems

A/B testing

Experiment design

Fairness & safety

Live-service ML

Vertex AI

SageMaker

Ray

Kafka

Flink

Redis

Cost-aware ML deployment

Tools

Vertex AI

SageMaker

Ray

Kafka

Flink

Redis

Job description

• As a Sr. Principal ML Engineer within the Central Product team, you will define and drive the modeling architecture that powers personalization, matchmaking, and social experiences across the player ecosystem - in and around the game
• Working alongside Product Leaders, Software Engineers & Data Engineers who lead foundational data systems for social graph, presence, chat, and matchmaking telemetry, you will lead the AI and modeling layer that transforms this data into intelligent, adaptive, and fair experiences for our players
• Your work ensures that every player connection - from friend recommendations to lobby matchmaking and in-game social features - feels meaningful, fair, and personalized through responsible, scalable machine learning systems
• Define and lead the modeling architecture that powers player personalization, matchmaking, social graph recommendations, and community discovery
• Develop models for churn model, revival models
• Drive multi-objective optimization frameworks balancing fairness, latency, diversity, and experience quality
• Establish and standardize evaluation protocols (match quality, satisfaction metrics, toxicity mitigation)
• Build real-time inference systems for personalized content, store offers, matchmaking and player interactions at scale
• Partner with the Data Engineers to integrate low-latency data pipelines and feature stores into online model serving
• Lead adoption of contextual bandits, reinforcement learning, and graph ML for adaptive, session-aware personalization
• Drive experimentation systems for live-service optimization (player retention, engagement, satisfaction)
• Work in lockstep with the Product leaders, Software Engineers & Data Engineers to define data schema, pipeline, and feature requirements that support advanced modeling
• Collaborate deeply with Data Engineers to align ML and data-system architecture
• Co-define standards for data schema design, feature lineage, and model observability
• Jointly drive automation and reliability across the data + ML lifecycle — from ingestion to inference
• Ensure shared governance for real-time player data, ensuring quality, security, and compliance
• Define Responsible AI standards for matchmaking and social systems — including fairness, transparency, and explainability
• Implement bias mitigation and trust calibration mechanisms to ensure equitable player experiences
• Partner with Research and Player Dynamics teams to ensure ethical alignment and reduce emergent negative behaviors
• Lead post-launch evaluations of algorithmic impact on community health and player sentiment
• Drive org-wide model optimization standards - latency, throughput, memory efficiency
• Architect systems for multi-model orchestration (e.g., skill, preference, and toxicity models working in concert)
• Define telemetry standards for online model observability and drift detection
• Partner with platform teams to optimize inference cost and hardware utilization
• Mentor senior ML engineers and data scientists, strengthening system design and experimentation practices
• Collaborate with Data Engineering, Game Engineering, and Player Insights teams to define unified data contracts
• Represent the ML discipline in cross-functional design reviews, ensuring data-driven decision making
• Contribute to hiring, interview calibration, and craft council development for ML excellence

Benefits

• Healthcare: Medical, dental, and vision plans that cover you as well as your spouse/domestic partner and children.
• Family Care: Life insurance, parental leave, plus short and long-term disability.
• Open Paid Time Off: In addition to holidays, a 2-week end of year break, and a 1-week mid-year break, Rioters are trusted to take the time they need throughout the year.
• Retirement: Riot matches retirement contributions so you can continue to play games long after you retire.
• Play Fund: Riot’s annual play fund allows Rioters to broaden their knowledge of the games that matter to players and the community.
• Donation Matching: Riot matches donations of time and money to nonprofits to double down on support.

• Proficiency in PyTorch, TensorFlow, JAX, and modern data/serving frameworks (Ray, Kafka, Flink, Redis)
• Track record of defining cross-team ML standards and leading technical direction
• 15+ years in Machine Learning or Applied AI; 3+ years in a principal or staff-level technical leadership role
• Deep expertise in graph ML, reinforcement learning, and representation learning
• Proven experience in real-time, large-scale ML systems - matchmaking, recommendations, or personalization
• Strong understanding of A/B testing, experiment design, and player experience metrics
• Background in game development, player behavior modeling, or social ecosystems
• Experience in trust & safety, toxicity detection, or community health models
• Familiarity with Vertex AI, SageMaker, or internal orchestration systems for real-time inference
• Demonstrated success integrating ML systems with live-service game backends