Principal Backend Engineer

Flagship Pioneering, Inc.; Cambridge (MA); On-site; USD 188,000 - 259,000; Full time

Benefits offered by this job

Health care coverage

Annual incentive program

Retirement benefits

Broad range of other benefits

Job summary

Extuitive, based in Cambridge, MA, is a Flagship Pioneering–backed startup reimagining backend systems for the AI era. We seek a Principal Backend Engineer to lead design, build, and scale core services and data pipelines, with strong third‑party integrations and security focus.

You will drive architecture, ensure reliability, and contribute to technical strategy in a fast‑paced, high‑impact environment. Equity, growth and collaboration opportunities await.

Qualifications

• 8+ years of backend engineering experience.
• Experience with high velocity agentic coding under strict security requirements.
• Bachelor’s degree in Computer Science, Software Engineering, or equivalent.
• Strong backend languages: Node.js/TypeScript, Go, Python, or similar.
• Designing scalable distributed systems, microservices, event-driven architectures.
• Experience with REST/GraphQL APIs, webhooks, rate-limited services.
• Proficiency with SQL/NoSQL databases, data pipelines, performance optimization.
• Familiarity with AWS, GCP and containerized systems (Docker, Kubernetes).
• Strong testing, CI/CD, and observability practices.

Responsibilities

• All things AI agents – from harness selection to prompt optimization and eval system.
• Own Core Backend Systems – scalable services, APIs, and platform infrastructure.
• Build and Maintain Large-Scale Data Pipelines – high-volume data processing.
• Lead Third-Party Integrations – reliable external vendor connections.
• Influence Architecture & Best Practices – coding standards, CI/CD, observability.
• Wear Multiple Hats – support DevOps and platform needs as needed.

Skills

8+ years experience

High velocity agentic coding

Backend-focused architecture

Node.js/TypeScript

Go

Python

REST/GraphQL

SQL/NoSQL databases

AWS/GCP cloud

Docker/Kubernetes

CI/CD & testing

Education

Bachelor's degree in CS/SE

Tools

Node.js/TypeScript

Go

Python

REST/GraphQL

Docker

Kubernetes

AWS

GCP

SQL/NoSQL

Job description

COMPANY DESCRIPTION

Extuitive is a Flagship Pioneering–backed startup reimagining product innovation for the AI era. Our mission is to revolutionize go to market for planning and execution for the agentic age. Based in Cambridge, MA, we operate like a special ops unit—fast-moving, data-driven, and relentlessly focused on impact.

THE ROLE

As a Principal Backend Engineer, you’ll be a technical leader responsible for architecting, building, and scaling the core backend systems that power our agentic platform. You’ll drive the design of high-throughput services, resilient data pipelines, real time agent clouds, and integrations with mission-critical third-party providers. You’ll translate complex requirements into robust, elegant systems that support rapid growth. You’ll be a key contributor to our technical strategy, helping evolve our platform architecture to maintain security and reliability as we scale.

KEY RESPONSIBILITIES

• All things AI agents – from harness selection to prompt optimization and eval system, you’ll work side by side with your teammates to deliver best in class agent experiences.
• Own Core Backend Systems – Design, build, and maintain scalable services, APIs, and platform infrastructure. Ensure reliability, observability, and maintainability.
• Build and Maintain Large-Scale Data Pipelines – Architect and operate high-volume, resilient data pipelines for ingestion, transformation, and analytics.
• Lead Third-Party Integrations – Build and maintain integrations with external vendors, ensuring reliability, observability, and long-term maintainability.
• Influence Architecture & Best Practices – Shape backend architecture, coding standards, testing frameworks, CI/CD pipelines, and operational excellence.
• Wear Multiple Hats – Support DevOps, troubleshooting, or other platform needs when necessary.

PROFESSIONAL EXPERIENCE & QUALIFICATIONS

• 8+ years of backend engineering experience.
• Experience with high velocity agentic coding under strict security requirements.
• Bachelor’s degree in Computer Science, Software Engineering, or equivalent practical experience.
• Strong expertise in backend languages and frameworks (Node.js/TypeScript, Go, Python, or similar).
• Experience designing scalable distributed systems, microservices, and event-driven architectures.
• Deep experience with third-party integrations, REST/GraphQL APIs, webhooks, and rate-limited services.
• Proficiency with SQL/NoSQL databases, data pipelines, and performance optimization.
• Familiarity with cloud platforms (AWS, GCP) and containerized/deployed systems (Docker, Kubernetes).
• Strong testing, CI/CD, and observability practices.
• Comfortable working in a fast-paced, evolving environment with minimal oversight.

Nice to Have

• Experience building and shipping features quickly in early-stage startups.
• Exposure to multiple backend domains (analytics, payments, notifications, workflow orchestration).
• Hands-on experience with serverless or edge architectures for rapid iteration.
• Familiarity with low-friction integrations with third-party tools and SaaS platforms.
• Track record of scaling systems from small MVPs to production-ready services.
• Comfort with ambiguity and making trade-offs between speed, quality, and maintainability.

ABOUT FLAGSHIP PIONEERING:

Flagship Pioneering invents and builds platform companies, each with the potential for multiple products that transform human health, sustainability and beyond. Since its launch in 2000, Flagship has originated more than 100 companies. Many of these companies have addressed humanity’s most urgent challenges: vaccinating billions of people against COVID-19, curing intractable diseases, improving human health, preempting illness, and feeding the world by improving the resiliency and sustainability of agriculture.

Flagship has been recognized twice on FORTUNE’s "Change the World" list, an annual ranking of companies that have made a positive social and environmental impact through activities that are part of their core business strategies and has been twice named to Fast Company’s annual list of the World’s Most Innovative Companies. Learn more about Flagship at www.flagshippioneering.com.

At Flagship, we accept impossible missions to enable bigger leaps. Our core values guide us through uncertainty and toward lasting impact.

We are an equal opportunity employer

All qualified applicants will be considered for employment without regard to race, color, religion, sex, sexual orientation, gender identity, national origin, disability, protected veteran status, or any other characteristic protected by law.

We recognize that great candidates often bring unique strengths without fulfilling every qualification. If you have some of the experience listed above but not all, please apply anyway. We are dedicated to building diverse and inclusive teams and look forward to learning more about your background and interest in Flagship.

The salary range for this role is $188,000 - $258,500. Compensation for the role will depend on a number of factors, including a candidate’s qualifications, skills, competencies, and experience.

Extuitive, Inc. currently offers

• healthcare coverage
• annual incentive program
• retirement benefits
• a broad range of other benefits

Compensation and benefits information is based on Extuitive, Inc.’s good faith estimate as of the date of publication and may be modified in the future.