SpaceX 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, SpaceX is actively developing the technologies to make this possible, with the ultimate goal of making life multiplanetary and expanding consciousness to the stars.
SpaceXSI is building Super Intelligence to help humanity understand the universe. Our teams are building the full Super Intelligence stack: from our Colossus supercomputers, to Grok models, to our suite of applications, including Grok Bot, Grok Build, Grok Imagine, Grok Voice, and X. We're creating a powerful flywheel where more compute trains better models, better models power more useful products, and what we learn from people using those products shapes what we build next.
At SpaceXSI we are building the high-performance inference platform that serves Grok to millions of users every day. As a Software Engineer, Training/Inference (C++), you will design and optimize large-scale model serving systems end-to-end. You will own everything from distributed infrastructure – global KV cache, continuous batching, load balancing, auto-scaling – to deep low-level optimizations, including GPU kernels, quantization, speculative decoding, and tail latency. This is a high-impact role where your work directly determines how fast and reliably users interact with Grok at massive scale.
RESPONSIBILITIES:- Architect and implement scalable distributed infrastructure for model serving (load balancing, auto-scaling, batch scheduling, global KV cache)
- Optimize latency and throughput of model inference under real production workloads
- Build and operate high-concurrency serving systems with excellent tail latency and high reliability at the scale required to serve millions of users
- Benchmark, fine-tune, and accelerate inference engines (including low-level GPU kernel work and code generation)
- Develop custom tools to trace, replay, and fix issues across the full stack — from orchestration down to GPU kernels
- Create robust CI/CD infrastructure for seamless endpoint deployment, image publishing, and inference engine updates
- Accelerate research on scaling test-time compute, RL rollout, and model-hardware co-design for next-generation systems
- Bachelor’s degree in computer science, computer engineering, or science discipline
- 5+ years of experience with low-level system programming experience in C/C++ or Rust
- Experience with large-scale, high-concurrent production serving
- Experience with GPU inference engines (e.g., vLLM, SGLang, Triton, TensorRT-LLM)
- Strong background in system optimizations: batching, caching, load balancing, parallelism
- Low-level inference optimizations: GPU kernels, code generation
- Algorithmic inference optimizations: quantization, speculative decoding, distillation, low-precision numerics
- Experience with testing, benchmarking, and reliability of inference services
- Experience designing and implementing CI/CD infrastructure for inference
$220,000 - $357,000 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.
SpaceXSI is an equal opportunity employer. For details on data processing, view our Recruitment Privacy Notice.
Skills Required
- Bachelor's degree in computer science, computer engineering, or a science discipline
- 5+ years of low-level system programming experience in C, C++, or Rust
- Experience with large-scale, high-concurrency production serving
- Experience with GPU inference engines such as vLLM, SGLang, Triton, or TensorRT-LLM
- Strong background in batching, caching, load balancing, and parallelism optimization
- Experience with GPU kernels and code generation
- Experience with quantization, speculative decoding, distillation, or low-precision numerics
- Experience testing, benchmarking, and improving inference-service reliability
- Experience designing and implementing CI/CD infrastructure for inference
xAI Compensation & Benefits Highlights
The following summarizes recurring compensation and benefits themes identified from responses generated by popular LLMs to common candidate questions about xAI and has not been reviewed or approved by xAI.
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Healthcare Strength — Healthcare is described as comprehensive, including medical, dental, vision, mental health support, and fertility benefits. Additional protections such as disability and life insurance, plus HSA/FSA options, are also outlined.
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Equity Value & Accessibility — Equity is positioned as a core component of total rewards alongside high base salaries for technical roles. Pre‑IPO stock grants are highlighted as enabling participation in potential company growth.
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Leave & Time Off Breadth — The package includes flexible or generous PTO, paid holidays, and paid sick days. Company materials also describe flexible vacation policies intended to help manage fast‑paced workloads.
xAI Insights
What We Do
Understand the Universe
