Senior Product Engineer

About Langfuse

Open Source LLM Engineering Platform that helps teams build useful AI applications via tracing, evaluation, and prompt management (mission, product). We are now part of Click House.

We're building the "Datadog" of this category; model capabilities continue to improve, but building useful applications is really hard, both in startups and enterprises.

Largest open source solution in this category: trusted by 19 of the Fortune 50, >2k customers, >26M monthly SDK downloads, >6M Docker pulls.

We joined Click House in January 2026 because LLM observability is fundamentally a data problem and Langfuse already ran on Click House. Together we can move faster on product while staying true to open source and self-hosting, and join forces on GTM and sales to accelerate revenue.

Previously backed by Y Combinator, Lightspeed, and General Catalyst.

We're a small, engineering-heavy, and experienced team in Berlin and San Francisco. We are also hiring for engineering in EU timezones and expect one week per month in our Berlin office (how we work).

Your work will have an outsized impact.

Everything you build is open source (MIT-licensed) and immediately visible. Langfuse has 21,900+ Git Hub stars and our SDKs are downloaded 23M+ times per month. When you ship a new feature the community notices in Git Hub issues, on X, and in our community channels.

Product engineers at Langfuse are the people who deliver new features end-to-end to our users. You own the product thinking from understanding the user problem to deciding what to build to shipping the solution.

You will also have direct exposure to how cutting‑edge LLM applications are built. The users you serve are some of the best and most ambitious software engineers leveraging Langfuse to improve their applications. Deeply understanding the problems they solve will help you design the best possible product and along the way make you an expert on LLM engineering yourself.

• Own features end-to-end: from talking to users, to writing the spec, to shipping the code and docs, to writing the changelog post with your name on it. To give you a sense: recent features a single engineer owned include the Langfuse for Agents release (new trace views, agent graphs, semantic span labels), the Type Script SDK v4 rewrite on Open Telemetry, and the hosted MCP server for prompt management.
• Work across the full stack: and we mean full. Our surface area is wide:
  React frontend, Next.js backend, Click House analytics, Python and Type Script SDKs, public docs, Terraform modules, and more. You'll touch whatever the feature needs. One week you might be writing a new Click House query for cost analytics, the next you're designing an SDK API, the next you're building a new React view for agent traces.
• Talk to users constantly: jump on calls, respond in community channels, and route support requests. At Langfuse, support is how we build conviction about what to build next. Our handbook says it best: support by engineers is a core value proposition.
• Write public documentation about the features you own. At Langfuse, docs are product.
• Ship publicly during Launch Weeks: we've run four Launch Weeks so far, dropping a new feature every day for a week. Engineers present the features they built to the community.

• Someone who has built features or even entire products from scratch end-to-end
• Experience building and shipping user‑facing products end-to-end, ideally in Type Script/React and with exposure to data‑intensive backends
• Someone who can manage projects themselves. You know how to develop strong conviction about what to build and how to ship it.
• Taste for great developer experience: you care about API design, UI details, and clear documentation
• Interest in open source software and genuine excitement about talking to developers about their problems
• Thrives in a small, accountable team where your output is visible and matters
• CS or quantitative degree preferred

• Experience with Click House, analytics databases, or building complex data visualizations
• Former founder or early startup experience
• Contributions…