Senior Full-Stack Engineer (+ Equity) at AI-native startup with YC backing

This is a role that TechTree is recruiting for on behalf of one of our clients.TechTree is an AI-driven recruitment platform working with high-growth companies.When you apply, our AI Agent matches you not just to this role, but to other relevant opportunities across our network, so one application can unlock multiple roles.About The RoleWe're seeking a Senior Full-Stack Engineer (Backend-Leaning) to join a dynamic AI-native team in San Francisco. This role involves end-to-end ownership of features, from conception to implementation, in a fast-paced environment. You'll play a crucial part in developing a personal AI assistant for knowledge workers, impacting how users interact with technology.What You'll Be DoingOwn features from conception through architecture, implementation, shipping, and iteration.Handle backend-heavy work with infrastructure and DevOps responsibilities.Engage directly with users to translate feedback into experiments and improvements.Develop AI systems, understanding agent loops and model interaction patterns.What We're Looking ForSenior-level experience as a full-stack engineer with a backend focus.Strong systems design skills and infrastructure ownership.Experience building AI-enabled products and understanding agentic workflows.Ability to operate independently with high agency in an ambiguous environment.Compensation & BenefitsSalary: $200,000 – $240,000 depending on experience.Meaningful equity included.About The CompanyThis company is a 12–14 person AI-native team based in San Francisco, focused on building a personal AI assistant for knowledge workers. They have raised $30M in seed funding from Spark Capital, Felicis, and Y Combinator, marking one of the largest seed rounds in YC history. The team consists of former founders, CTOs, and high-agency builders, emphasizing high ownership and a major public launch.What is TechTree?TechTree combines AI agents with a human support team to give candidates a better, more transparent hiring experience.Our AI Agent gets to know your background, experience, and what you're optimising for. It continuously matches you to live roles across our network where there's genuine alignment, not just keyword overlap.Our Human Team is there to support you through the process:Answer questions about roles, process, and next stepsAdd context when something in your background isn't obviousHelp unblock stalled processes or unclear feedbackMake sure you're not left guessing, ghosted, or wasting timeWe only post real jobs. Every role on TechTree is a live, active hire.If you apply: you'll be considered for this role, you may also be matched to other relevant roles, and if there's no fit, we won't spam you.