Founding Full-Stack Engineer

About the Role We're a Y Combinator–backed EdTech startup on a mission to help people acquire languages and connect across cultures — and we're hiring a Founding Full-Stack Engineer to join our small, tight-knit founding team in San Francisco. This is a rare opportunity to shape the product, architecture, and engineering culture from the ground up at a fast-growing, mission-driven company in the language learning space. You'll work in-person with the founders every day, own large swaths of the codebase, and ship features end-to-end — from backend services and data models all the way through mobile UI and deployment. If you thrive at the intersection of great craft, AI-driven product experiences, and genuine mission, this role is for you. What You'll Do Collaborate in-person with the founding team daily in San Francisco. Own large parts of the codebase across mobile, web, backend, infrastructure, and AI. Ship full end-to-end product features — from backend logic through UI to 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 while maintaining a strong commitment to quality, craftsmanship, and reliability. What We're Looking For Must-haves (dealbreakers): 3+ years of professional software engineering experience delivering end-to-end features across mobile, web, and backend systems. Strong experience building backend services in Go (Golang) with PostgreSQL , including data modeling and performance optimization. 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 understanding of at least two compiled languages, including Go and one other (e.g., Swift, Kotlin, C++, Java, 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. Excellent 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 provider 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 one; familiarity with immersion-first language learning is a big plus. Compensation & Benefits Salary: $150,000 – $200,000 USD annually Meaningful early-stage equity Visa sponsorship available when needed Location This role is fully on-site in San Francisco, CA . You'll work in person with the founding team every day. Candidates must be willing and able to commit to full-time, in-person work in San Francisco.