Backend Engineer at Langfuse (W23) €70K - €160K EUR Open source LLM engineering platform Berlin, BE, DE Full-time US citizenship/visa not required 3+ years About Langfuse Langfuse is building open-source observability and product analytics for LLM applications. We help engineers and companies understand how customers use their LLM applications and how they can improve on them. Have a look at our website and especially technical docs to learn more. About the role Skills: Python, TypeScript In short: We are hiring a (senior) Backend Engineer to make our systems and infra keep up with our globally growing user base and billions of monthly events to process. About Langfuse We are building the fastest growing open-source LLM engineering platform. We help engineers and enterprises build and run LLM applications at scale. We've raised $4m from Y Combinator, Lightspeed and General Catalyst. Thousands of teams and engineers use Langfuse daily Thousands are joining every month We're a small, focused team working from Berlin, Germany. What you'll do Past projects you would have led: Optimizing the latency of complex database queries in Postgres or Clickhouse Adding Redis queues and a worker container to our stack to execute async tasks Come up with a new architecture for our ingestion pipeline with the goal to increase throughput and cut cost Explore different CH schemas and materialized views and test for different query patterns. Re-building our SDKs to use OTEL under the hood Write Terraform code to add new infra components Tech Stack You should be familiar with a majority of these but we trust that you can pick up a new language/framework quickly. Frontend and Backend in Typescript (including Express, NextJs, Tailwind, Prisma, tRPC) Clickhouse, Postgres, Redis, S3 Client facing SDKs in Python and Typescript What we're looking for Experience in maintenance of highly reliable and scaling infrastructure 3+ years of experience in backend or full-stack development Excited about open source software Experience with the trade offs of handling large amounts of data Hard worker and thrive working in a small and accountable team A CS/quantitative degree is preferred Bonus Experience with or interest in SDK design and DX ML/AI experience Impressive achievements from previous careers or side projects Previous startup or founding experience Why Langfuse? You are joining really early Strong Product Market Fit! We are building a very small but highly capable team Only hiring Engineering in foreseeable future Strong customer & revenue growth Building picks and shovels for the hottest AI companies Building for very sophisticated technical users Competitive salary & equity Performance and learning focused culture Everyone on the team says: "best place I've ever worked at" How we work Engineering based in Berlin ( we aim for 4-5 days in the office ) No more than 2 short scheduled meetings per week Extreme ownership & autonomy how and what to work on Links Project you could have built: Infrastructure Evolution Blog Post Our codebase: GitHub Repository Ben Kuhn on Impact, Agency and Taste Who we are & how we work Technology https://github.com/langfuse/langfuse/ Stack: Frontend and Backend in Typescript (T3 Stack including NextJs, Tailwind, Prisma, tRPC), Postgres, Client facing SDKs in Python and Typescript Interview Process Fill out application & We screen your application Call: Intro & CV deep dive with CTO (45min) Call 2: Technical Deep Dive (90min) Onsite Super Day ( half or full day in Berlin Office ) Meet the other founders (short calls) Decision & Offer We expect you to have used Langfuse (you can sign up for a free account here) and skimmed through our documentation and public content.