Senior Systems Engineer

About Blacksmith - We started by building infrastructure to run CI workloads really fast. Our first product helps companies run GitHub Actions substantially faster and cheaper by owning and operating our own global fleet of bare-metal machines rather than renting generic cloud VMs. - Today, we orchestrate tens of millions of Firecracker VMs each week, running CI for 10,000+ companies and tens of millions in ARR. We’ve grown 20x so far in 2026. - We operate thousands of bare-metal machines across multiple regions, regularly schedule 300k+ vCPUs concurrently, and run a petabyte-scale Ceph cluster that we manage ourselves. - We’ve raised $125M from Seed to Series C, led by Sequoia, Google Ventures (GV) & Peak XV Partners, and we’re intentionally building a small, but exceptional team. - Blacksmith was founded by a team with deep systems and scaling experience, including building search/ads infrastructure at Faire, and operating large distributed systems at Cockroach Labs. Our GTM is led by Jon Boyer, formerly Head of Sales at Zapier. - We're now extending the same CI infrastructure into a broader platform: running agent sandboxes at scale and building our own background coding agent on top of it. You are a good fit if you - Have developed and scaled distributed systems and enjoy digging into performance and reliability issues across the filesystem, network, and storage stack. - Are comfortable writing and debugging in C, C++, Go, Rust, or Zig, and care deeply about efficiency, correctness, and safety at the systems level. - Are excited by the idea of self-hosting and managing infrastructure with build automation and configuration management tools (e.g., Ansible, Puppet, Chef). - Have familiarity with distributed storage systems like Ceph or MinIO, or are eager to get hands-on with them. - Have 5+ years of software development experience, ideally in performance-critical or distributed environments. - Enjoy working in person 5 days a week in NYC with a small, tight-knit team. - Thrive in the ambiguity of an early-stage startup and are energized by building from first principles. Bonus - You’ve dabbled in your own side hustles or start-up projects. - You’re comfortable creating new processes and iterating on them quickly. Compensation and benefits - Medical, Vision, and Dental insurance. - Competitive base + equity. - 401K match. - Unlimited PTO. - Annual offsite. - Early-exercise stock options - 12 weeks fully paid parental leave (US)