Sr. Model Engineer, RL Training Framework

SpaceXSI · Palo Alto, CA · $180,000 - $400,000 SpaceXSI was founded under the belief that a future where humanity is out exploring the stars is fundamentally more exciting than one where we are not. Today, SpaceXSI is actively developing the technologies to make this possible, with the ultimate goal of making life multiplanetary and expanding consciousness to the stars. The RL infrastructure team is looking for an engineer to help develop our RL training framework. Responsibilities: Design and implement the systems backing all RL workloads at SpaceXSI, from small scale ablations to production training runs Profile, debug, and optimize end-to-end training performance Improve scalability and observability of the RL stack Basic Qualifications: Experience writing production-quality code in Python, PyTorch, JAX, Rust, or C++ Experience training large models (e.g., pre-training, post-training, fine-tuning, or RL training of neural networks with 1B+ parameters) Preferred Skills and Experience: Experience building, debugging, and optimizing efficiency of large-scale distributed systems Experience with large scale LLM training infrastructure Experience with RL numerics Strong knowledge of reinforcement learning techniques Comfortable diving into unfamiliar areas and solving problems at all levels of the stack Compensation and Benefits: $180,000 - $400,000 USD Base salary is just one part of our total rewards package at SpaceXSI, which also includes equity, comprehensive medical, vision, and dental coverage, access to a 401(k) retirement plan, short & long-term disability insurance, life insurance, and various other discounts and perks.