Senior Product Engineer About LangfuseOpen Source LLM Engineering Platform that helps teams build useful AI applications via tracing, evaluation, and prompt management (mission, product). 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).Why Product Engineering at LangfuseYour work will have an outsized impact.Everything you build is open source (MIT-licensed) and immediately visible. Langfuse has21,900+ 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 usersyou serve are some of the best and most ambitious software engineers leveraging Langfuse toimprove their applications. Deeply understanding the problems they solve will help you designthe best possible product and along the way makes you an expert on LLM engineering yourself.You will grow at Langfuse byOwn 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 TypeScript SDK v4 rewrite on OpenTelemetry, 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, 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 so far, dropping a new feature every day for a week. Engineers present the features they built to the community.What we’re looking forSomeone who has built features or even entire products from scratch end-to-endExperience building and shipping user-facing products end-to-end, ideally in TypeScript/React and with exposure to data-intensive backendsSomeone 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 documentationInterest in open source software and genuine excitement about talking to developers about their problemsThrives in a small, accountable team where your output is visible and mattersCS or quantitative degree preferredBonus points:Experience with ClickHouse, analytics databases, or building complex data visualizationsFormer founder or early startup experienceContributions to popular open source projectsML/AI background or familiarity with the LLM framework ecosystemNo candidate checks all boxes. If you feel you are a good fit for this role, please go ahead and apply.ProcessWe can run the full process to your offer letter in less than 7 days (hiring process).Tech StackWe run a TypeScript monorepo: Next.js on the frontend, Express workers for background jobs, PostgreSQL for transactional data, ClickHouse for tracing at scale, S3 for file storage, and Redis for queues and caching. You should be familiar with a good chunk of this, but we trust you'll pick up the rest quickly (Stack, Architecture).How we shipLink to handbookWe trust you to take ownership (ownership overview) for your area. You identify what to build, propose solutions (RFCs), and ship them. Everyone here thinks about the user experience and the technical implementation at the same time. Everyone manages their own Linear.You're never alone. Anyone from the team is happy to go into a whiteboard session with you. 15 minutes of shared discussion can very much improve the overall output.We implement maker schedule and communication. There are two recurring meetings a week: Monday check-in on priorities (15 min) and a demo session on Fridays (60 min).Code reviews are mentorship. New joiners get all PRs reviewed to learn the codebase, patterns, and how the systems work (onboarding guide).We use AI as much as possible in our workflows to make our users happy. We encourage everyone to experiment with new tooling and AI workflows.Why Langfuse (now part of ClickHouse)This role puts you at the forefront of the AI revolution, partnering with engineering teams who are building the technology that will define the next decade(s).This is an open-source devtools company. We ship daily, talk to customers constantly,