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 design, build, and operate Colossus from the ground up. This includes the massive GPU clusters, high-speed interconnect fabric, and the software that makes it all work at unprecedented scale. Colossus powers Grok and our frontier AI models with a custom, high-performance datacenter network that delivers ultra-low latency and massive bandwidth across hundreds of thousands of GPUs.
As a Software Engineer on the Colossus Networking team, you will develop the core networking software that maximizes the performance and reliability of our datacenter fabric. Your work will directly impact training efficiency, model convergence, and the speed at which we can push the frontier of AI.
Our engineers own the full lifecycle of their software — from design and implementation to deployment, monitoring, and iteration based on real-world performance at scale. You will solve hard problems in distributed systems, high-performance networking, and real-time control of one of the largest AI supercomputers on Earth.
RESPONSIBILITIES:- Develop routing and traffic-engineering algorithms for the Colossus high-performance datacenter network
- Develop highly reliable, real-time software designed to run on the switches that form the backbone of our low-latency, high-bandwidth AI training fabric
- Participate in and lead architecture, design, and code reviews
- Develop prototypes and run experiments to validate key design decisions at both small and full-cluster scale
- Build tools for software development, deployment, data analysis, visualization, and testing across virtualized environments, hardware-in-the-loop setups, and live production clusters
- Deploy reliable software updates through continuous integration and release systems with rigorous testing and monitoring
- Bachelor’s degree in computer science, engineering, math, or technical discipline
- 5+ years of professional software development experience in lieu of a degree
- Development experience in C or C++
- Strong professional experience writing high-performance C/C++ in production environments
- Experience developing, debugging, and deploying software that runs at scale in real-world systems
- Deep knowledge of networking protocols (UDP, TCP/IP, RDMA, etc.), distributed systems, and large-scale datacenter fabrics
- Background in real-time systems, high-performance computing, low-latency networking, or resource-constrained environments
- Creative problem-solving ability with exceptional analytical skills and strong engineering fundamentals
- Excellent written and verbal communication skills
- Ability to thrive in a fast-paced, dynamic environment with evolving requirements
- Experience with security considerations in large-scale distributed systems
$200,000 - $375,000 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, engineering, mathematics, or another technical discipline
- 5+ years of professional software development experience may substitute for a degree
- Development experience in C or C++
- Strong professional experience writing high-performance C/C++ in production environments
- Experience developing, debugging, and deploying software at scale in real-world systems
- Deep knowledge of networking protocols such as UDP, TCP/IP, and RDMA
- Knowledge of distributed systems and large-scale datacenter fabrics
- Background in real-time systems, high-performance computing, low-latency networking, or resource-constrained environments
- Creative problem-solving ability and exceptional analytical skills
- Excellent written and verbal communication skills
- Ability to thrive in a fast-paced, dynamic environment with evolving requirements
- Experience with security considerations in large-scale distributed systems
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
