Summary
Y Combinator profiles Blacksmith, a startup that builds infrastructure to run continuous integration (CI) checks far faster. The company recently raised a roughly $66 million Series C at a $1 billion valuation led by Sequoia, and says it has grown 20x in the last year.
The founders explain why agentic coding tools have shifted the bottleneck in software development. Developers can now generate far more code, but shipping it depends on validating it, which means waiting on CI. Blacksmith’s answer is a cloud designed specifically for CI workloads, which behave more like video games than typical server tasks because they depend on the speed of a single thread. The company uses gaming CPUs, initially rented from a German data center provider known for hosting Minecraft and Call of Duty servers, and now buys capacity at the megawatt scale. It also speeds up builds by moving cache artifacts close to compute nodes.
The video covers how the three founders, who had no DevOps background, won their first 200 customers by leaning on friends for logo rights and doing direct outreach to CTOs. It highlights LangChain, whose developers previously waited 15 to 20 minutes for compute on GCP and now wait 10 to 15 seconds on Blacksmith. A YC partner who invested in both the initial round and Series A also shares their perspective.
📺 Source: Y Combinator · Published November 02, 2026
🏷️ Format: Interview
