Senior Backend Software Engineer, Observability & Evals Platform (LangSmith)

About LangChain:

At LangChain, our mission is to make intelligent agents ubiquitous. We provide the agent engineering platform and open source frameworks developers need to ship reliable agents fast.

Our open source frameworks, LangChain and LangGraph, see over 90+ million downloads per month and help developers build agents with speed and granular control. LangSmith offers observability, evaluation, and deployment for rapid iteration, enabling teams to transform LLM systems into dependable production experiences.

LangChain is trusted by millions of developers worldwide and powers AI teams at companies like Replit, Clay, Cloudflare, Harvey, Rippling, Vanta, Workday, and more.

About the role:

In person 5 days/week in San Francisco, Boston, MA, New York, Amsterdam, or London.

We are looking for a Senior Backend Engineer to join us. In this role you will be 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:

• 5+ 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:

• We offer competitive compensation that includes base salary, meaningful equity, and benefits such as health and dental coverage, flexible vacation, a 401(k) plan, and life insurance. Actual compensation will vary based on role, level, and location. For team members in the EU and UK, we provide locally competitive benefits aligned with regional norms and regulations.

• Annual salary range: $170,000- $195,000