Senior Backend Software Engineer, Observability & Evals Platform; LangSmith

Senior Backend Software Engineer, Observability & Evals Platform (Lang Smith)

Lang Chain (Lang Smith) seeks a Senior Backend to build backend systems powering Lang Chain's observability and evals platform. This in-person role works 5 days/week in San Francisco, Boston, MA, New York, Amsterdam, or London.

As a Senior Backend Engineer, you will design, develop, and maintain backend services and APIs that support Lang Smith’s tracing, monitoring, and evaluation workflows. You will collaborate with full‑stack engineers, product managers, and designers to roll out new features while ensuring systems are performant, reliable, and maintainable.

• Design, develop, and maintain backend services and APIs to support Lang Smith’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.

• 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, Click House) and cloud platforms (AWS, GCP, Azure).
• Strong communication skills, with the ability to collaborate cross‑functionally.
• Customer centricity and ownership mentality.

• Competitive base salary and equity; annual range: $170,000–$195,000.
• Health and dental coverage, flexible vacation, 401(k) plan, and life insurance.
• Benefits aligned with regional norms for EU and UK team members.