Product Engineer

Langfuse is building the open-source LLM engineering platform to help engineers understand how users interact with their LLM applications and improve them. The company has raised a $4M seed round from Y Combinator, Lightspeed and General Catalyst, with thousands of engineers already using the platform.

As a Product Engineer, you'll be responsible for adding new features and building out existing ones. The core functionality involves ingesting millions of events daily via SDKs, visualizing data in the UI, and running async workflows. You'll work closely with the CTO and CEO on technical and product decisions.

Key projects include:

• Owning major feature releases during launch weeks
• Building and maintaining model-based evaluations
• Developing the LLM Playground
• Managing core integrations with Llama Index, Langchain, OpenAI
• Implementing new integrations like Posthog

The tech stack includes:

• Frontend and Backend in Typescript (T3 Stack with NextJs, Tailwind, Prisma, tRPC)
• Clickhouse and Postgres databases
• Client SDKs in Python and Typescript

You'll join as a core team member with significant ownership and impact. The role offers:

• Early-stage startup experience building open source developer tools
• End-to-end product ownership
• Opportunity to shape technical architecture
• Potential for growth into management
• Work from Berlin office with small, high-performing team
• Culture focused on autonomy and learning

The ideal candidate has:

• 2+ years full-stack development experience
• Strong ownership mentality and drive
• Interest in open source and developer tools
• Ability to engage with users and understand their needs
• Experience with or interest in UX/UI design and DX
• Optional: ML/AI experience or early-stage startup experience

The role is based in Berlin with 4-5 days in-office, offering €70K - €130K salary and 0.10% - 0.35% equity. Join a growing team building the future of LLM development tools.