(Senior) Backend Engineer

About Langfuse

• Open Source LLM Engineering Platform that helps teams build useful AI applications via tracing, evaluation, and prompt management (mission, product)

• We have the chance to build 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: >2k customers, >14M monthly SDK downloads, >6M docker pulls

• We raised money from world class investors (Y-Combinator, Lightspeed, General Catalyst) and are default alive by making more money than we spend

• We’re a small, engineering-heavy, and experienced team in Berlin and San Francisco (how we work)

About the Role

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.

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.

• see our tech stack

• see our architecture

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

Hiring Process

We can run this process in less than 7 days.

1. Fill out application

2. We screen your application

3. Jump on a intro call with our CTO

4. Technical Deep Dive interview

5. Super Day ( half or full day in Berlin Office )

6. Meet the other founders (short calls)

7. Decision & Offer

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