Member of Technical Staff - ML Infrastructure Engineer, RL Post-training

Preference Model, Inc.; San Francisco (CA); On-site; USD 180,000 - 280,000; Full time

Benefits offered by this job

Competitive cash & equity ( >90th %ile

Ownership and autonomy

Work alongside senior staff from topML

Health, vision, dental, benefits

401K match

Lunch onsite

Weekly snacks

Visa sponsorship & relocation support

Job summary

Preference Model, Inc. is seeking Senior ML Infrastructure Engineers in San Francisco to build the infrastructure powering post-training on large language models.

You will design and scale compute, scheduling, and data pipelines, develop core ML framework primitives, and implement evaluation, monitoring, and deployment tooling.

Join a frontier research team backed by strong funding, with equity, visa sponsorship, and a fast-moving startup culture.

Qualifications

• Strong software engineering fundamentals and production-grade LLM infra experience.
• Transformers, distributed training, and inference libraries experience.
• Hands-on with RL training frameworks and high-throughput workloads.
• Distributed systems knowledge and cloud/container orchestration.
• Proficiency in PyTorch or JAX for ML workflows.

Responsibilities

• Design, build, and scale compute, scheduling, and data infra for post-training research.
• Develop ML framework primitives and internal tooling to speed reproducible experiments.
• Create evaluation, monitoring, logging, debugging, and automated deployment tooling.
• Collaborate with Research Engineers to translate research needs into infrastructure requirements.

Skills

Strong software engineering

Production-grade LLM infra

Transformers & distributed training

RL training frameworks

Distributed systems

Cloud platforms (AWS/GCP)

Kubernetes

Docker

PyTorch or JAX

Data pipelines

Tools

Kubernetes

Docker

Terraform

vLLM tooling

Job description

About Us

Preference Model is a superintelligence data research company. We build RL environments for training capable, better-aligned superintelligences.

Almost every aspect of how a model behaves is shaped by the reward signals it's trained on. The biggest problem with AIs today is that they don't always do what we intend. Sometimes that's because they aren't capable enough, and sometimes it's because they aren't aligned. Both problems come down to the training objectives.

We're trying to address both of these issues in the most direct, highest leverage way available to us, which today means researching how to build RL environments better, not just for the AIs of today but for the AIs as they will be when they outsmart us.

Over the past year, we've built RL environments for several frontier labs, and we're backed by $16M in seed funding led by a16z. Our founding team has previous experience on Anthropic’s data team building data infrastructure, and datasets behind Claude.

About the Role

Frontier research moves only as fast as its infrastructure permits. Building solid infrastructure is foundational to our mission of pushing self-directed learning as far as it can go.

We are looking for Senior ML Infrastructure Engineers to build the infrastructure and systems that power the frontier of post-training on large language models. This role involves building scalable infrastructure to enable high-throughput systems and shape how our research is run, bringing us closer to models that can train themselves on what they aren't yet good at.

What You Will Do

• Design, build, and scale the compute, scheduling, and data infrastructure that powers post-training research on our in-house RL environments




• Develop and maintain core ML framework primitives and internal tooling that researchers rely on daily, accelerating reproducible experimentation and reducing time from idea to result




• Build evaluation and benchmarking infrastructure, monitoring, logging, and debugging tooling, and automated testing and deployment systems, so failures are caught early and infrastructure stays reliable as it scales




• Partner directly with Research Engineers to translate research needs into infrastructure requirements, and ship fast in response to their feedback
  

What We are Looking For

• Strong software engineering fundamentals and hands-on experience building production-grade LLM inference and training infrastructure (ideally from the ground up)




• Experience building LLM training/inference internals such as transformers, distributed training, and working on inference libraries like vLLM, SGLang, Megatron




• Experience working on RL training frameworks like Slime, veRL, Ray Train, SkyRL, Miles




• Significant experience and understanding of distributed systems principles, and have hands-on experience with cloud platforms (AWS, GCP) and container orchestration (Kubernetes), building systems for high-throughput, low-latency workloads




• Have experience with data engineering tools and building robust, scalable data pipelines




• Proficiency in core ML frameworks such as PyTorch or JAX




• Can balance production rigor with the pace of fast-moving research, and communicate infrastructure tradeoffs clearly to researchers who aren't infra specialists

What We Offer:

• Competitive cash and equity compensation (>90th percentile)




• Ownership and autonomy in a fast moving startup environment




• Opportunity to work alongside senior and staff engineers from frontier labs and infrastructure companies, plus top ML engineers




• Health, vision, dental, benefits




• 401K match




• Lunch provided everyday onsite




• Weekly snack orders




• Visa sponsorship & relocation support available

We value diverse perspectives and experiences. If you're excited about this role but don't check every box, we still encourage you to apply.