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

LangChain•Cambridge, MA

21h•$180,000 - $240,000•Onsite

About The Position

LangChain is seeking a Senior Backend Engineer to join their growing engineering team in Boston. This role involves building the backend systems that power LangSmith, LangChain’s observability and evals platform. The engineer will work on core services enabling customer developer teams 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 valuable. LangChain's mission is to make intelligent agents ubiquitous, providing the foundation for agent engineering and helping developers move from prototypes to production-ready AI agents. The company has raised $125M at Series B and is experiencing accelerating growth. Their platform includes LangSmith, open-source frameworks like LangChain and LangGraph, and the LangSmith Engine. They boast significant open-source downloads and a large customer base, including many Fortune 500 companies.

Requirements

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.
Strong communication skills, with the ability to collaborate cross-functionally.
Customer centricity and ownership mentality

Nice To Haves

Familiarity with fullstack or frontend engineering
Familiarity with performance tuning
Familiarity with debugging production issues
Experience with database systems (Postgres, Redis, Clickhouse)
Experience with cloud platforms (AWS, GCP, Azure)

Responsibilities

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.