Software Engineer

Software Engineer – Platform / Applied AIOnsite, San FranciscoI'm working with a fast-growing AI company building the expert reasoning and data infrastructure used by frontier AI labs to improve their models. They capture the step-by-step reasoning, judgment and decision-making of verified domain experts and turn it into high-quality training data, evaluation environments, agent trajectories and RL infrastructure. The company has scaled at an exceptional pace; reportedly becoming YC's fastest unicorn ever after raising at a $3.2B valuation, around 10x its previous valuation in just five months. It is backed by leading venture investors and already generates significant revenue while operating with a lean, high-caliber engineering team. This is a high-ownership role for someone who wants to build core platform infrastructure from the ground up in a fast-moving environment. You'll work on: Architecting and scaling high-throughput data pipelines Building complex data-capture workflows across web and desktop Designing backend and platform infrastructure in Python Working with distributed systems, queues, caching and search infrastructure Building production systems across cloud environments Owning projects end-to-end from architecture through deployment Working directly with the founding team to define technical direction and ship quickly