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

About Us

At LangChain, our mission is to enable every company to own its intelligence. We believe agents will transform how companies operate, and we're building the foundation to make that future possible. Our open-source harnesses and LangSmith platform give developers and enterprises the infrastructure to run, improve, and govern agents at scale.

We've raised $460M to date, with our most recent funding round valuing the company at $3B, backed by leading investors including Sequoia, Benchmark, IVP, and CapitalG. As we continue to expand our platform and tackle some of the hardest challenges in agent engineering, every team member has the opportunity to make a meaningful impact and help shape both our technology and the future of the industry.

More than 7,000 organizations rely on LangSmith, from fast-growing startups to Fortune 500 enterprises, including NVIDIA, Bridgewater, LinkedIn, Workday, and Rippling. We're just getting started on making high-performing agents easier to build and manage at scale.

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. If you want to define what great AI observability looks like at production scale, this is where that work gets done.

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. While the focus is on backend feature development, familiarity with fullstack or frontend engineering, performance tuning, and debugging production issues would be valuable.

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

Annual salary range: $170,000- $235,000

Compensation Philosophy:

We offer competitive compensation that includes base salary, variable compensation for relevant roles, meaningful equity, benefits, and perks.

We are hiring for this role across a range of scope, and the compensation band reflects that. Your offer depends on what we learn about your impact, craft, leadership, and communication during the interview process. We will tell you early where you’re tracking and talk comp with you before offer stage. Team members in the EU, UK, and APAC receive locally competitive benefits aligned with regional norms and regulations.

Benefits

Benefits include medical, dental, and vision coverage, flexible vacation, a 401(k) plan, meals on in-office days in the US and more.