Full Stack Engineer

Direct message the job poster from Moss (YC F25) We’re on a mission to make conversational AI agents think and respond at the speed of human conversation, everywhere they run. Today’s retrieval stack wasn’t built for real-time reasoning, so we’re building Moss: the semantic search layer for the AI-agent era. Backed by YC, we’re making every AI product feel instantaneous, deeply personalized, and actually useful in the real world. We're looking for a senior Full-Stack Engineer (6+ years experience) who thrives on solving complex problems and will not wait for someone else to tell what to do. You'll work directly with the founding team to architect core systems, build complex infrastructure, and shape the future of agentic experiences. Must-Have Requirements 6+ years building and shipping production software in a product-focused environment. Strong expertise in TypeScript and modern front-end frameworks (React / Next.js). Experience designing and owning backend services (Node.js, Rust, Go, or similar). Strong fundamentals in performance optimization, caching, and profiling. Experience with cloud infrastructure (AWS, Azure, Cloudflare, or GCP) and observability. Ability to move fast in ambiguous environments - high ownership and bias for action. Nice-to-Have Skills Familiarity with vector search, embedding pipelines, or real-time retrieval systems. Experience building developer tools or production SDKs. Knowledge of API versioning, usage metering, billing, and multi-tenant auth. Contributions to open-source infra / web performance libraries. Key Responsibilities Architect and build core services that power Moss at scale. Own end-to-end product surfaces: APIs, dashboards, developer experience, and tooling. Optimize Moss for latency, resource efficiency, and reliability across runtime environments. Work directly with customers and design partners to shape product direction. Contribute to the Moss engineering culture with strong code quality, fast iteration, rapid learning. Equity: Meaningful stock options. Location: San Francisco (preferred), flexibility for exceptional talent. Work: In person collaboration as a small, high-trust, founder-led team. Seniority level Mid-Senior level Employment type Full-time Referrals increase your chances of interviewing at Moss (YC F25) by 2x #J-18808-Ljbffr Moss (YC F25)