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.