Lead Full-Stack Engineer

Golden Gate Recruiting is hiring a Lead Full-Stack Engineer for ThirdBrain Labs, an a16z-backed seed-stage AI research lab in San Francisco built with experts from Stanford, UC Berkeley, NYU, Princeton, Waymo, and Palantir! Location: San Francisco, CA (on-site) Compensation: $200K to $240K base + meaningful early equity ThirdBrain Labs is a research and post-training team unlocking the next billion specialized models. They help organizations access, use, and continuously improve their proprietary intelligence in one click, at a fraction of the cost. Customers unlock competitive private models with ThirdBrain's in-context continual learning and research infrastructure, customizing models in a fraction of the time and labor. Backed by a16z, the team brings applied AI deployment and scaling experience from Palantir, Coatue, Temasek, Citadel, and frontier AI research. About The Role ThirdBrain is looking for a Lead Full-Stack Engineer to help turn its research and model infrastructure into reliable, elegant products that customers can use every day. This role sits close to the core product surface: model access, customer workflows, model artifacts, reliability, observability, internal tools, and the systems that let teams use and improve their private intelligence. As the company moves toward releasing models and public artifacts more frequently, you will help build the product and infrastructure layer that makes that cadence possible. You should be comfortable across backend and frontend, with especially strong instincts for reliability, product clarity, and fast iteration. This is a great fit for someone who likes building in close partnership with researchers, customers, and founders. What You Will Do • Build product surfaces for accessing, comparing, monitoring, and improving private and third-party models. • Improve the reliability, performance, and observability of the Mandala Model API beta and related platform systems. • Build backend services for model access, usage tracking, customer configuration, artifact delivery, model metadata, decision-system workflows, and internal operations. • Create clean, useful interfaces for customers and internal teams to inspect model behavior, cost, performance, and outputs. • Partner with ML and research engineers to turn prototypes into durable product workflows. • Build tools that support frequent releases of models, evals, demos, reports, and customer-facing artifacts. • Own systems end to end, from database schema and API design to frontend interaction details. • Help set engineering standards for a small, fast-moving technical team. You May Be A Fit If You • Have shipped full-stack products used by real customers. • Are strong in backend engineering and comfortable building clean frontend experiences. • Have experience with TypeScript, React, Python, Postgres, cloud infrastructure, APIs, queues, observability, and production debugging. • Care about reliability and user experience in equal measure. • Can take ambiguous product or research needs and turn them into working systems. • Have good taste in abstractions and know when to keep the system simple. • Are excited to work near frontier model systems, evals, private AI infrastructure, and products that expose powerful research clearly. • Communicate clearly and enjoy working with researchers, customers, and product-minded founders. Nice To Have • Experience building developer platforms, model APIs, inference gateways, data products, observability tools, or enterprise AI workflows. • Experience with authentication, permissions, billing and usage metering, rate limits, SLAs, or customer-facing infrastructure. • Experience working in early-stage startups or high-ownership engineering teams. • Familiarity with LLM APIs, evals, agents, retrieval, fine-tuning, or model serving. • Design sensibility for dense technical products where clarity matters more than flash. What They Value Engineers who are curious, honest, and allergic to cargo-cult thinking. People who ask why, test assumptions, and care whether the thing they built actually works. The best person for this role will help make ThirdBrain's research usable: fast, reliable, understandable, and valuable to customers building competitive intelligence inside their organizations. Excited? Apply here or reach out to Rachel at rachel@goldengaterecruiting.com!