Sr. Software Engineer, Kernels/CUDA (C++)

xAI•Palo Alto, CA

About The Position

SpaceXSI is building Super Intelligence to help humanity understand the universe. The company is developing the full Super Intelligence stack, including its Colossus supercomputers, Grok models, and applications. As part of the Compute Infrastructure team, the Sr. Software Engineer will help build one of the world’s largest AI supercomputers. The role owns both the GPU supercomputer and the platform layer running on it, working across low-level GPU kernel optimization, Linux kernel internals, large-scale orchestration, and virtualization. The work aims to make training and inference faster, more reliable, and more scalable, directly accelerating Grok’s training and AI progress.

Requirements

5+ years of experience with low-level system programming in C/C++.

Nice To Haves

Deep low-level systems programming experience in C/C++/PTX/SASS.
Strong experience with large-scale GPU clusters or distributed compute infrastructure at production scale.
Hands-on experience with GPU kernel optimization, including CUTLASS, custom kernels, and Nsight profiling.
A track record of building or running high-performance infrastructure for AI workloads, including training or inference platforms.
Ability to reason from first principles and optimize for both memory-bound and compute-bound scenarios.

Responsibilities

Design, build, and optimize massive GPU clusters for extreme-scale training and inference workloads.
Develop and tune low-level CUDA kernels, including GeMM and Attention, using CUTLASS, Tensor Cores, and Nsight for maximum performance.
Profile, debug, and eliminate bottlenecks across GPU memory hierarchy, networking fabric, filesystems, and multi-GPU operation.
Collaborate closely with AI research teams to deliver production-grade performance and scalability.