Founding Software Engineer

About the Role A Y Combinator-backed AI creative tools startup is hiring its founding software engineer . You'll work directly with the founding team to shape the technical foundation of an AI-powered motion design platform — turning what once took hours into minutes for professionals and video teams worldwide. This is a high-ownership, zero-to-one role at a company with strong early traction and rapid revenue growth. What You'll Do Partner with the founders to deliver user-centric product features from concept to production. Own end-to-end full-stack development with a focus on scalable architecture. Build and optimize agentic LLM systems, including tool-calling, multi-step reasoning, and MCP protocols. Design and implement comprehensive LLM evaluation frameworks — automated benchmarks, human-in-the-loop validation, and A/B testing. Optimize LLM inference performance, cost efficiency, and latency across multiple model architectures. Develop a high-performance motion graphics engine. Drive architectural decisions to support growth to millions of users. What We're Looking For Required: 2+ years of software engineering experience with strong CS fundamentals. Proficiency in TypeScript (dealbreaker); hands-on experience with React.js, Next.js, PostgreSQL, GCP, and/or AWS. Proven experience building or integrating LLMs — tool-calling, multi-step reasoning, and MCP protocols. Experience designing LLM evaluation frameworks with automated benchmarks, human-in-the-loop validation, and A/B testing. Demonstrated ability to deliver end-to-end full-stack features at scale. Background in startups or early-stage environments with a strong ownership mindset. Ability to optimize LLM inference for performance, cost, and latency across multiple model architectures. Nice to Have: Experience in AI creative tools, motion graphics, or animation-adjacent products. High learning velocity and ability to ramp quickly in a fast-moving environment. Compensation & Benefits Salary: €80,000 – €160,000 annually, depending on experience. Equity participation as a founding team member. No visa sponsorship available. Location This role is on-site in Berlin, Germany . Candidates must be willing and able to work from the Berlin office full-time. #J-18808-Ljbffr CLERA