Preference Model Senior ML Infrastructure Engineer to build scalable compute, scheduling, and data infrastructure powering post-training research on RL environments. Develop core ML framework primitives and internal tooling.
Responsibilities
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.
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
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
Qualification
Required
Experience running end-to-end LLM post-training pipelines of models sizes at least 7B
Proficiency in Python and PyTorch or JAX
Experience with at least one modern RL training framework
Experience building and operating ML infrastructure at scale
Preferred
Experience evaluating model outputs and building reward or evaluation signals
Stay current on post-training research and translate papers into running code
Strong opinions about structuring RL training code for reproducibility and fast iteration
Balance research exploration with engineering rigor