Senior Backend Software Engineer, AI Observability & Evals Platform (LangSmith)

LangChain; Cambridge (MA); On-site; USD 180,000 - 240,000; Full time

Benefits offered by this job

Medical insurance

Dental insurance

Vision insurance

Flexible vacation

401(k) plan

Meals on in-office days

Job summary

LangChain is seeking a Senior Backend Engineer to join our Boston-based team. You will build the backend systems powering LangSmith, focusing on observability, evaluation, and scalable data services.

The role emphasizes backend feature development with opportunities to engage in frontend and full-stack considerations as needed. Ideal candidates have 4+ years in backend engineering, strong Python/Go API design skills, and experience with high-throughput systems and cloud platforms.

Qualifications

• 4+ years of backend engineering experience.
• Proficiency in Python and/or Go and API design.
• Experience with high-throughput, mission-critical systems and cloud platforms.

Responsibilities

• Design, develop, and maintain backend services and APIs for LangSmith’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 data.
• Ensure system reliability through testing, monitoring, and alerting practices.
• Troubleshoot production issues and implement long-term fixes with root-cause analysis.
• Create and maintain technical documentation including system design and API references.
• Work with full-stack engineers, product managers, and designers to roll out new features.

Skills

Backend engineering

Python

Go

API design

High-throughput systems

Postgres

Redis

Tools

Postgres

Redis

AWS/GCP/Azure

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 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 based onsite in Boston, MA.

We are looking for a Senior Backend Engineer to join our growing engineering team in Boston. In this role you will be building the backend systems that power LangSmith, LangChain’s observability and evals platform. You will work on the core services that allow our customer's developer teams to monitor and evaluate their AI applications at scale. While the focus is on backend feature development, familiarity with fullstack or frontend engineering, performance tuning, and debugging production issues would be valuable.

What You'll Do:

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

What You'll Bring:

• 4+ years of professional experience in backend engineering working on highly complex products
• Proficiency in one or more backend languages/frameworks, ideally Python and/or Go
• Strong understanding of API design and building reliable data services.
• Experience with high-throughput, mission-critical systems.
• Demonstrated ability to optimize backend services for performance and reliability.
• Experience with database systems (Postgres, Redis, Clickhouse), and cloud platforms (AWS, GCP, Azure) would be a bonus.
• Strong communication skills, with the ability to collaborate cross-functionally.
• Customer centricity and ownership mentality

Compensation:

Annual salary range: $180,000- $240,000

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.