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

LangChain; United States; On-site; USD 180,000 - 240,000; Full time

Benefits offered by this job

Medical, dental, vision

401(k)

Equity

Flexible vacation

In-office meals in US

Job summary

LangChain is seeking a Senior Fullstack Engineer for LangSmith, our observability and evaluation platform. You will shape the technical direction across Go/Python backend and React/TypeScript frontend, working with enterprise customers and internal teams.

We value at least 5 years of software engineering experience on complex platform products, API design, and high-performance data apps. The role offers a competitive USD salary and meaningful equity, with in-office days in the US.

Qualifications

• 5+ years of software engineering on complex platform products.
• Backend in Go or Python with frontend in React + TypeScript.
• Strong understanding of database systems (Postgres, Redis).
• Experience designing and scaling APIs in high-performance data apps.

Responsibilities

• Lead the technical architecture and implementation of key LangSmith features across Go, Python, and TypeScript.
• Collaborate with product and design teams to iterate on new features.
• Mentor junior engineers and drive timelines while maintaining high standards.
• Write clean, maintainable, well-tested code and ship rapidly.

Skills

5+ years experience

Go backend

Python backend

React frontend

TypeScript

API design

Tools

PostgreSQL

Redis

Job description

About Us

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. We began as widely adopted open-source tools and have grown to also offer a platform for building, evaluating, deploying, and operating agents at scale.

With $125M raised at Series B from IVP, Sequoia, Benchmark, CapitalG, and Sapphire Ventures, we’re at a stage where we’re continuing to develop new products, growth is accelerating, and all team members have meaningful impact on what we build and how we work together. LangChain is a place where your contributions can shape how this technology shows up in the real world.

Today, our platform includes LangSmith (Observability, Evaluation, Deployment, Fleet, and Sandboxes), our open source frameworks (LangChain, LangGraph, and Deep Agents), and the newly launched LangSmith Engine for autonomous agent improvement. We have 100M+ monthly open source downloads, 6,000+ active LangSmith customers, and 5 of the Fortune 10 use LangSmith in production (+ 35% of the Fortune 500 overall), including teams at Klarna, Clay, Coinbase, Workday, Lyft, Cloudflare, Harvey, Rippling, Vanta, LinkedIn, Monday.com, Nvidia, and Bridgewater.

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.

What You Will Do:

• 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

What You Bring:

• 5+ years of experiencein 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: $180,000-$240,000 USD

Compensation Philosophy:

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

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