Senior Fullstack Engineer, AI Observability & Evals Platform

Langchain
Boston, MA
On-site

In the 12 months to 30 Jun 2026, Langchain filed 12 H-1B positions classified as Software Developers. Source: U.S. Department of Labor, LCA disclosure data. A record of filings already made, not a commitment to sponsor.

Who this role is best for

A natural match if you have experience building scalable AI platforms and working in a fullstack capacity.

Best fit for

  • Candidates with experience in building scalable AI systems and fullstack development in Go, Python, and Typescript
    — “Lead the technical architecture and implementation of key product features for LangSmith, working across our entire Go, Python, and Typescript stack.”
  • Individuals who have shaped technical direction for enterprise-grade platforms and engaged directly with top-tier customers
    — “you'll have the opportunity to shape the technical direction of our platform while working closely with our enterprise customers”

Things to consider

  • Onsite requirement in Boston, MA may limit remote flexibility despite the company's growth focus
    — “This role is onsite 5 days/week in Boston, MA”
  • The role demands a high level of ownership and direct customer engagement
    — “Strong ownership mindset”

How to stand out

  • Highlight your experience in fullstack development with Go, Python, and React + Typescript in your resume and interviews
    — “Fullstack engineering experience with Go or Python on the backend and React + Typescript on the frontend.”
  • Showcase your ability to shape technical direction and influence product development through past projects
    — “you'll have the opportunity to shape the technical direction of our platform”
  • Emphasize your background in high-performance API design and database systems like Postgres and Redis
    — “Experience designing and scaling APIs, preferably in a high-performance, data-intensive application”
  • Demonstrate strong communication skills by providing examples of working with enterprise clients or cross-functional teams
    — “Strong communicator with the ability to collaborate closely with various internal stakeholders and engage directly with our top-tier customers”
  • Mention any prior work with AI/LLM-powered applications or observability platforms to align with the bonus criteria
    — “Bonus: Experience with AI/LLM-powered applications, developer tools, or observability platforms”
Pace · Fast PacedCollaboration · HighAutonomy · HighDecision Impact · Team

Derived from job-description analysis by Serendipath's career intelligence engine.

What success looks like

  • lead technical architecture and implementation of key product features
  • collaborate closely with product and design teams
  • drive aggressive project timelines
  • write clean, maintainable, and well-tested code
Typical background
5+ years of experience in software engineeringfullstack engineering experience with Go or Python on the backend and React + Typescript on the frontend

Skills & requirements

Required

GoPythonTypeScriptReactPostgreSQLRedisAPI DesignDatabase SystemsHigh-performance Data-intensive ApplicationsClean CodeMaintainable CodeWell-tested CodeCommunicationOwnership Mindset

Preferred

Ai/llm-powered ApplicationsDeveloper ToolsObservability Platforms

Stack & domain

GoPythonTypeScriptReactPostgreSQLRedisAPI DesignHigh-performanceData-intensiveAI ObservabilityLlm-powered ApplicationsDeveloper ToolsObservability PlatformsCommunicationCollaborationOwnershipAttention-to-detailProblem-solvingAIMLObservabilityEvaluationDeploymentFleetSandboxesLangchainLangsmith

About the role

Original posting from Langchain via Ashby

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 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 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.

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.
  • Help 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 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

Compensation

  • Annual salary range: $175,000-$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.

Source: Langchain careers (Ashby)

Similar roles

More roles at Langchain