Senior Product Engineer, Fullstack

About the Role Keystone AI's product is what developers touch every day — Playground, Model Garden, Fine-Tuning, File Management, Batch Processing, Model Evals. These surfaces are how users experience the platform, and they need to be fast, intuitive, and something developers genuinely love using. That's what this role is about. We're growing the Product Engineering team and looking for a fullstack engineer who's motivated by shipping things users genuinely value — not features that just look good in a slide deck. You'll plug directly into new and existing workstreams and start shipping quickly, working across our core product surfaces to improve existing capabilities and build new ones. This is a high-ownership role on a small, fast-moving team, where one strong engineer moves the needle visibly. You'll see your work in production, instrument and measure it, and use that to shape what comes next. Responsibilities Ship improvements and new capabilities across Keystone AI's core product surfaces — Playground, Model Garden, Fine-Tuning, File Management, Batch Processing, and Model Evals Own projects and features end-to-end, from data model and API integration through the user interface Collaborate closely with other engineers to build clean, typed, reusable interfaces in our web application Instrument and measure what you ship — add product analytics, monitor system health, and prove users are getting value with data Work across design, product, and engineering to ship things that unlock user value Raise the bar on frontend and fullstack quality across the team through code review and collaborative architecture decisions Requirements 4–7 years of experience building and shipping real product to real users Strong JavaScript/TypeScript fundamentals; TypeScript experience highly valued Strong React expertise in a large-scale, production environment Full-stack fluency: you connect the dots from data model to API design to state management to the UI, and know how to make the right call at each layer in service of clean, maintainable code and an intuitive user experience A pragmatic approach to engineering — you know when to move fast and when to slow down, and you make that call based on user value Curiosity about AI and LLMs — you want to understand the models and products you're building on top of, not just the code around them Adept at building and improving agentic workflows, with good judgment for when to lean on AI and when not to Cross-functional "we ship it" mentality — no narrow ownership, no finger-pointing Next.js, Tailwind, and shadcn/ui experience is a plus Familiarity with product analytics (e.g., Amplitude) and systems monitoring (e.g., Grafana) is a plus Experience with CI/CD workflows is a plus Experience with a backend language like Go or Python About Keystone AI Keystone AI is a research-driven artificial intelligence company. We believe open and transparent AI systems will drive innovation and create the best outcomes for society, and together we are on a mission to significantly lower the cost of modern AI systems by co-designing software, hardware, algorithms, and models. We have contributed to leading open-source research, models, and datasets to advance the frontier of AI, and our team has been behind technological advancement such as FlashAttention, Hyena, FlexGen, and RedPajama. We invite you to join a passionate group of researchers in our journey in building the next generation AI infrastructure. Compensation We offer competitive compensation, startup equity, health insurance and other competitive benefits. The US base salary range for this full-time position is: $154000 - 221000 + equity + benefits. Our salary ranges are determined by location, level and role. Individual compensation will be determined by experience, skills, and job-related knowledge. Equal Opportunity Keystone AI is an Equal Opportunity Employer and is proud to offer equal employment opportunity to everyone regardless of race, color, ancestry, religion, sex, national origin, sexual orientation, age, citizenship, marital status, disability, gender identity, veteran status, and more. Please see our privacy policy at https://www.together.ai/privacy .