Principal Engineer, LLM (Platform and Tooling)

About Upstart At Upstart, we're united by a mission that matters: to radically reduce the cost and complexity of borrowing for all Americans. Every day, we bring creativity, experimentation, and advanced AI to reshape access to credit, helping millions move forward financially with clarity and confidence. As the leading AI lending marketplace, we partner with banks and credit unions to expand access to affordable credit through technology that's both radically intelligent and deeply human. Our platform runs over one million predictions per borrower using more than 1,800 signals, powering smarter, fairer decisions for millions of customers. But the numbers only hint at the impact. Every idea, every voice, and every contribution moves us closer to a world where credit never stands between people and their financial progress. We're proudly digital-first, giving most Upstarters the flexibility to do their best work from wherever they thrive, alongside teammates across 80+ cities in the US and Canada. Digital-first doesn't mean distant. We're intentional about in-person connection through team onsites, planning sessions, and moments that spark creativity and trust. And whether you choose to work primarily from home or collaborate in-person from one of our offices in Columbus, Austin, the Bay Area, or New York City (opening Summer 2026), you'll have the support to work in the way that works best for you. If you're energized by tackling meaningful problems, excited to innovate with purpose, and motivated by work that truly matters, we'd love to hear from you. The Team Upstart's GenAI Core Platform team builds the foundational Platform that democratizes access to generative AI across the company. As a Principal Engineer - GenAI/LLM, you will provide technical leadership across multiple cross-functional teams, shaping the vision, architecture, and adoption strategy for our new GenAI platform for Engineers and non-Engineers alike. You will work closely with engineering leaders, ML researchers, and product stakeholders to ensure Upstart can scale the safe, efficient, and responsible use of LLMs across all business domains. This role goes beyond delivery. It is about setting long-term direction, de-risking our most ambitious AI initiatives, and raising the bar for technical excellence across the organization. In short, you will have a direct influence and impact on how we enable and implement GenAI and LLMs internally at Upstart. How You'll Make an Impact Define and drive the multi-year technical roadmap for the Core GenAI Platform, influencing adoption and alignment across several engineering teams Collaborate with CTO/VP-level and above leadership to influence business strategy with technical insight Lead architecture and design of large-scale, mission-critical systems for model inference, orchestration, and compliance Identify and solve systemic technical risks that impact the entire company and business-critical AI initiatives Represent Upstart internally and externally as a thought leader in GenAI systems through executive reviews, cross-company forums, and industry venues Establish operational standards for GenAI integrations, ensuring security, fairness, and reliability at scale Build high-leverage, generalizable platform components that meaningfully accelerate the productivity of engineers across Upstart Mentor senior engineers, other principal engineers, and shape the growth of future technical leaders, fostering a culture of learning and excellence Minimum Qualifications Bachelor's degree in Computer Science, Engineering, or Mathematics, or a related field (or its equivalent) + 8 years of experience Deep expertise in LLM-specific infrastructure such as inference optimization (quantization, ONNX, streaming). Ability to design scalable RAG architectures and manage the lifecycle of models from experimentation to high-availability production environments including vector databases. Proven experience building robust, automated evaluation pipelines using both heuristic metrics and 'LLM-as-a-judge' frameworks to ensure model accuracy and safety. Hands-on experience with LLM toolchains such as LangChain, LlamaIndex, or OpenAI APIs Experience designing and operationalizing ML/LLM platforms at scale, including optimization for cost, latency, and reliability and the platform infrastructure needed to support them. Deep Expertise in best practices and risks for GenAI including hallucination mitigation, fairness, explainability, and data privacy Preferred Qualifications 12+ years of experience and 5+ leading cross functional technical initiatives Proven ability to execute or guide model fine-tuning and alignment (RLHF/DPO) to optimize LLM performance for specialized consumer use cases and proprietary datasets. Full-stack engineering experience (Python, FastAPI, Kotlin, Spring, React/TypeScript, or similar) Deep expertise in backend systems and infrastructure technologies such as Kubernetes,