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

About Us

At LangChain, our mission is to make intelligent agents ubiquitous. We build the foundation for agent engineering in the real world, helping developers move from prototypes to production-ready AI agents that teams can rely on. Today, our platform includes LangSmith (Observability, Evaluation, Deployment, Fleet, and Sandboxes), our open source frameworks (LangChain, LangGraph, and Deep Agents), and the newly launched LangSmith Engine for autonomous agent improvement.

About the Team

The LangSmith team owns and builds LangChain's core platform for observability, evaluation, and production reliability of AI systems. From tracing and annotation to run rules, evaluations, and beyond, this team owns LangSmith end-to-end.

About the Role

This role is based onsite in Boston, MA. We are looking for a Senior Backend Engineer to join our growing engineering team in Boston. In this role you will be building the backend systems that power LangSmith, LangChain’s observability and evals platform. You will work on the core services that allow our customer's developer teams to monitor and evaluate their AI applications at scale.

What You'll 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.

What You'll Bring

• 4+ years of professional experience in backend engineering working on highly complex products.
• Proficiency in one or more backend languages/frameworks, ideally Python and/or Go.
• Strong understanding of API design and building reliable data services.
• Experience with high-throughput, 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) would be a bonus.
• Strong communication skills, with the ability to collaborate cross-functionally.
• Customer centricity and ownership mentality.