Senior Product Engineer

ABOUT LANGFUSE Open Source LLM Engineering Platform that helps teams build useful AI applications via tracing, evaluation, and prompt management (mission https://tracking.us.nylas.com/l/6d586a21a6fc4e1a8aacc7eb75882b72/0/82383757e54352130f65066e1b2fc4708aacab7897561bcb8000fe4c8a9c6a21?cache_buster=1761124921, product https://tracking.us.nylas.com/l/6d586a21a6fc4e1a8aacc7eb75882b72/1/b9fba3a93b6ffcc0f99ecda62767a17cc437fe8fe0b16181d1c43c1391212e3d?cache_buster=1761124921). We are now part of ClickHouse. 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 ClickHouse in January 2026 because LLM observability is fundamentally a data problem and Langfuse already ran on ClickHouse. 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 https://langfuse.com/handbook/how-we-work/principles). WHY PRODUCT ENGINEERING AT LANGFUSE Your work will have an outsized impact. Everything you build is open source (MIT-licensed) and immediately visible. Langfuse has 21,900+ GitHub stars and our SDKs are downloaded 23M+ times per month. When you ship a new feature the community notices in GitHub 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 makes you an expert on LLM engineering yourself. YOU WILL GROW AT LANGFUSE BY - Own features end-to-end: from talking to users, to writing the spec, to shipping the code and docs, to writing the changelog post https://langfuse.com/changelog with your name on it. To give you a sense: recent features a single engineer owned include the Langfuse for Agents https://langfuse.com/changelog/2025-11-05-langfuse-for-agents release (new trace views, agent graphs, semantic span labels), the TypeScript SDK v4 https://langfuse.com/changelog/2025-08-28-typescript-sdk-v4-ga rewrite on OpenTelemetry, and the hosted MCP server https://langfuse.com/changelog/2025-11-20-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, ClickHouse analytics, Python and TypeScript SDKs, public docs, Terraform modules, and more. You'll touch whatever the feature needs. One week you might be writing a new ClickHouse 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 https://langfuse.com/blog/2025-10-29-launch-week-4 so far, dropping a new feature every day for a week. Engineers present the features they built to the community. WHAT WE’RE LOOKING FOR - 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 TypeScript/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 Bonus points: - Experience with ClickHouse, analytics databases, or building complex data visualizations - Former founder or early startup experience - Contributions to popular open source projects - ML/AI background or familiarity with the LLM framework ecosyst