Y Combinator2 min read
Blacksmith hits $1B valuation running CI on gaming CPUs
Three engineers with no CI experience built a faster testing cloud for AI-generated code, raising $66M from Sequoia at a $1B valuation.
AI summary of “Fixing AI Coding's Bottleneck”
Key takeaways
- Blacksmith grew 20x in the past year and raised a $66 million Series C led by Sequoia at a $1 billion valuation.
- Founders had never built a CI pipeline before and found their edge by running CI on gaming CPUs instead of hyperscaler infrastructure.
- Blacksmith cut LangChain's CI wait time from 15–20 minutes on GCP to 10–15 seconds.
- The team scaled to many orders of magnitude more infrastructure with just 12 engineers by keeping the product's scope narrow.
- Blacksmith is now building autonomous QA tools that give developers evidence, like screenshots and video, that their code works.
Gaming CPUs solve the CI bottleneck
Blacksmith builds infrastructure to run continuous integration (CI) checks faster, a problem the founders approached as outsiders. "We were not platform engineers. We didn't work in DevOps. In fact, none of us had written a CI pipeline before," one founder said. The team, friends from Waterloo and Toronto, noticed that CI workloads resemble desktop applications or video games more than typical cloud workloads, since they depend on single-thread execution speed rather than parallelism. This insight led them to rent servers from a German data center provider known for hosting Minecraft and Call of Duty servers, before later buying megawatts of power directly from data center providers as they scaled.
An early investor said the gaming-CPU approach was unusual enough to surprise him: "No, we need to have buy like a hundred of these things and use them to compile. Like that that's where I was like, oh, that's kind of different." A key part of Blacksmith's technical approach is moving cache artifacts close to compute nodes to skip redundant work.
Fast adoption, lean team, and new product plans
Blacksmith's first 200 customers were hard to land; the founders started by asking friends for logo rights to build credibility, then personally called CTOs and VPs of engineering. Early customers were small, fast-moving companies with little red tape, switching to Blacksmith in one click. LangChain, previously on GCP, saw CI wait times drop from 15–20 minutes to 10–15 seconds after switching.
The company scaled from five people and a few hundred servers to a 30-person team with 12 engineers managing many orders of magnitude more infrastructure, which the team attributes to bespoke observability tooling and deliberately keeping the product's surface area small. A power surge in Phoenix once took out both primary and backup cooling systems at one data center, underscoring the need for geographic distribution. Looking ahead, Blacksmith plans to build autonomous QA tools that gather screenshots and video snippets as evidence that code changes work, aiming, as one team member put it, to let developers "bring shipping software as close as they can to their speed of thought."
Written by AI from the video's transcript. It can compress, misattribute or miss context — the original video is the source. Not investment advice.
