Senior Fullstack Engineer, AI Observability & Evals Platform

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.

This role is onsite 5 days/week in Boston, MA

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

* 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.

* Help drive aggressive project timelines while ensuring high engineering standards are being met.

* Lead by example in writing clean, maintainable, and well-tested code.

* 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 our top-tier customers

* Strong ownership mindset

* Bonus: Experience with AI/LLM-powered applications, developer tools, or observability platforms

* Annual salary range: $175,000-$240,000 USD

We offer competitive compensation that includes base salary, variable compensation for relevant roles, meaningful equity, benefits, and perks. Actual compensation and offerings will vary based on role, level, and location. Team members in the EU, UK, and APAC receive locally competitive benefits aligned with regional norms and regulations.

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

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