🚨 Software Engineer – Platform / Applied AI 📍 Onsite, San Francisco I’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 Requirements: ✅ Candidates from highly selective startups, quantitative engineering environments or similarly demanding technical teams are especially relevant ✅ Strong backend, platform or infrastructure engineering experience ✅ Strong Python experience, ideally with some full-stack capability ✅ Experience building scalable production systems or high-throughput data infrastructure ✅ Strong cloud and distributed systems fundamentals ✅ Evidence of personally owning and shipping substantial systems into production ✅ High agency and comfort operating in a fast-moving, low-process environment ✅ Exceptional academic and technical pedigree. The hiring bar is very high, with a strong preference for top computer science backgrounds ⭐ Experience in AI infrastructure, LLM evaluation, human-in-the-loop systems or applied AI is highly valuable 💰 Package: $260K–$290K base + meaningful equity + $200K–$400K bonus.