Founding Full-Stack Engineer

About the Role A Y Combinator–backed EdTech startup in San Francisco is hiring a Founding Full-Stack Engineer to join its founding team. The company is building an immersive, short-form video language-learning platform — backed by science and already trusted by hundreds of thousands of learners — that helps people achieve real conversational fluency. This is an in-person, early-stage role with meaningful equity. You'll work side-by-side with the founders every day, own large portions of the codebase, and have a direct hand in shaping product direction, engineering culture, and architecture from the ground up. The stack spans mobile, web, backend, infrastructure, and AI. What You'll Do Work in-person with the founding team daily in San Francisco. Own broad parts of the codebase across mobile, web, backend, infrastructure, and AI. Ship complete end-to-end product features — from backend logic through UI to production deployment. Build high-performance mobile experiences in React Native . Implement and maintain video streaming and HLS pipelines. Develop AI-driven learning experiences using LLMs and audio/video models. Build and maintain backend services in Go . Design data models, schemas, and performance optimizations in PostgreSQL . Improve developer tooling, CI/CD pipelines, and observability. Influence foundational architecture, engineering culture, product direction, and UX. Move fast without sacrificing quality, craftsmanship, or reliability. What We're Looking For Dealbreakers (must-haves): 3+ years of professional software engineering experience delivering end-to-end features across mobile, web, and backend systems. Experience building backend services in Go (Golang) with PostgreSQL , including data modeling and performance optimization. Proven experience delivering mobile apps using React Native (Expo) or native iOS/Android development. Required skills: Strong TypeScript fundamentals and solid foundations in HTML, CSS, JavaScript, and REST APIs. Deep knowledge of at least two compiled languages — Go plus one of Swift, Kotlin, C++, Java, or C#. Writes testable code with unit, integration, and end-to-end tests (mocks, pure functions). Experience with at least one scripting language (Python or Ruby) for tooling and automation. Comfortable with Unix-based systems, Git, and terminal workflows. Strong debugging skills using Chrome DevTools, RN profiler, or Xcode Instruments. Familiarity with video streaming (HLS) and building AI/LLM-driven features. Nice to have: Cloud experience (AWS, GCP, Azure, or DigitalOcean). CI/CD experience with GitHub Actions. Profiling and performance optimization experience. Prior startup or founder experience. Comfortable using AI development tools (Cursor, Copilot, GPT, Claude, etc.). Speaks multiple languages or is actively learning a spoken language; familiarity with immersion-first language learning is a plus. Compensation & Benefits Salary: $150,000 – $200,000 USD annually Equity: Meaningful founding-team equity package Visa sponsorship: Available when needed Location This role is fully on-site in San Francisco, CA . Candidates must be willing and able to work in person full-time. Visa sponsorship is available.