Senior Fullstack Software Engineer, AI Observability & Evals Platform (NY)

About LangChain

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 LangSmith Engine for autonomous agent improvement.

About the Role

We're looking for a Senior Fullstack Engineer for our commercial product LangSmith, an observability and evals platform. In this role, you'll have the opportunity to shape the technical direction of our platform while working closely with enterprise customers, developer end-users, and internal stakeholders.

Responsibilities

• Lead the technical architecture and implementation of key product features for LangSmith, working across our entire Go, Python, and TypeScript stack.
• Collaborate closely with product and design teams to iterate on new features.
• Mentor and guide more junior members of the team.
• Drive aggressive project timelines while ensuring high engineering standards are being met.
• Lead by example in writing clean, maintainable, and well-tested code.

Qualifications

• 5+ years of experience in software engineering working on complex platform products.
• Fullstack engineering experience with Go or Python on the backend and React + TypeScript on the frontend.
• Strong understanding of database systems, particularly Postgres and Redis.
• Experience designing and scaling APIs, preferably in a high-performance, data-intensive application.
• A “get stuff done” attitude - comfortable shipping fast and iterating based on user feedback.
• Strong communicator with the ability to collaborate closely with various internal stakeholders and engage directly with top-tier customers.
• Strong ownership mindset.
• Bonus: Experience with AI/LLM-powered applications, developer tools, or observability platforms.