Backend Engineer, Observability & Evals Platform

About LangChain:

LangChain was founded in early 2023 to help developers build context-aware reasoning applications. LangChain, open source software, is a framework that gives developers the building blocks to create production-ready applications with LLMs. LangSmith is our commercial, all-in-one SaaS platform that enables the end-to-end, development workflow for building LangChain and LLM-powered apps. LangSmith is now trusted by the best teams building with LLMs, at companies such as Airbnb, Rakuten, Elastic, Moody’s, Retool, and more. We’re a small team making an outsized impact (~5M monthly downloads and 50k+ applications powered ).

Backed by some of the best venture capitalists, Benchmark and Sequoia, we have big ambitions and are set up to build an enduring business.

About the role:

In person 5 days/week in San Francisco, CA or New York, NY

We are looking for a Backend Engineer to join our LangSmith team. In this role, you will be responsible for designing and building the backend systems that power LangChain’s observability and evals platform. You will work on the core services that allow developers to monitor and evaluate their AI applications at scale. While the focus is on backend feature development, familiarity with fullstack or frontend engineering, performance tuning, and debugging production issues would be extremely valuable.

What you will do:

• Design, develop, and maintain backend services and APIs to support LangSmith’s tracing, monitoring, and evaluation workflows.

• Collaborate on architectural decisions to ensure systems are performant and maintainable.

• Optimize storage and query performance for high-volume observability and evaluation data.

• Ensure system reliability through strong testing, monitoring, and alerting practices.

• Troubleshoot and resolve production issues, performing root-cause analysis and implementing long-term fixes.

• Create and maintain technical documentation, including system design and API references.

• Work closely with full-stack engineers, product managers, and product designers on rolling out new features.

How to be successful in this role:

• 3+ years of professional experience in backend engineering

• Proficiency in one or more backend languages/frameworks, ideally Python or Go

• Strong understanding of API design and building reliable data services.

• Experience with high-throughput or mission-critical systems.

• Demonstrated ability to optimize backend services for performance and reliability.

• Experience with database systems (Postgres, Redis, Clickhouse), and cloud platforms (AWS, GCP, Azure)

• Strong communication skills, with the ability to collaborate cross-functionally

• Customer centricity and ownership mentality

Compensation & Benefits:

• Competitive salary, equity & benefits package, commensurate with experience and aligned with stage of the company.

• Annual salary range: $155,000- $195,000