Principal Backend Engineer

About this role

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.

Recruitment & Staffing Agencies : Flagship Pioneering and its affiliated Flagship Lab companies (collectively, “FSP”) do not accept unsolicited resumes from any source other than candidates. The submission of unsolicited resumes by recruitment or staffing agencies to FSP or its employees is strictly prohibited unless contacted directly by Flagship Pioneering’s internal Talent Acquisition team. Any resume submitted by an agency in the absence of a signed agreement will automatically become the property of FSP, and FSP will not owe any referral or other fees with respect thereto.

Privacy Notice for Applicants: When you apply for a role at Flagship Pioneering or one of its portfolio companies, we collect and use personal information you provide (such as your name, contact details, work history, and application materials) to evaluate your application, communicate with you, and comply with legal obligations. Your application data is processed through Greenhouse, our applicant tracking system, and m

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