Fastapi Development Company Jobs in Massachusetts

Why You Should Join the Developer Infrastructure Team 

Our core focus is empowering engineers to ship code efficiently and safely. We own the build systems, dependency lifecycle, and platform infrastructure that underpin every engineer's daily workflow. As a Senior Software Engineer on this team, you will help define and execute the technical roadmap for Klaviyo's backend platform - from dependency management and major framework upgrades to developer productivity tools that reduce toil and accelerate velocity. By building and maintaining the foundational systems that keep our codebase healthy and scalable, you will play a pivotal role in ensuring every engineer at Klaviyo can move fast with confidence.

What You'll Achieve: Key Responsibilities

As a Senior Software Engineer for this team, you will drive the evolution of our developer platform across the organization:

• Dependency Management: Analyze, optimize, and secure backend and third-party dependencies across the codebase. Build frameworks for evaluating risk and ensuring our dependency graph stays healthy, performant, and maintainable.
• Platform Upgrades and Rollouts: Lead the planning and execution of major software releases and updates - from design through production rollout - including hands-on individual contribution throughout.
• Developer Productivity: Drive improvements across key cycle time metrics including PR CI speed, code review turnaround, and commit velocity. Relentlessly reduce toil and increase engineering efficiency across the organization.
• Set Engineering Standards: Contribute to the standards for code quality, dependency hygiene, and platform reliability that all teams follow.
• AI-Driven Strategy: Spearhead efforts to leverage AI within the platform lifecycle and use AI tooling to accelerate your own development work.
• Cross-Functional Collaboration: Partner with engineers, security teams, and stakeholders to gather requirements, resolve conflicts, and roll out platform changes that teams can adopt with confidence.
• Operational Excellence: Proactively monitor the health and reliability of the platform, diagnosing and resolving complex issues before they become critical incidents.

What Makes This Role Exciting:

• High-Leverage Work: You are not just building features; you are building the systems that determine how fast every engineer at Klaviyo can ship.
• Real Architectural Impact: You will influence the structure of a large, complex backend codebase and make decisions that scale with the company.
• Innovation at the Edge: You will have the autonomy to experiment with AI and emerging tooling to solve hard problems in dependency management, build performance, and developer experience.

Who You Are:

• Experienced Engineer: You have 5+ years of software engineering experience with strong computer science fundamentals and a focus on clean, maintainable, well-architected code.
• Analytical Problem Solver: You don't just fix symptoms - you hunt down root causes, implement systemic fixes, and build in safeguards to prevent recurrence.
• Platform-Minded: You are comfortable reasoning about distributed systems, dependency graphs, and the downstream impact of platform-level decisions across many teams.
• Technical Generalist: You can move across the stack when needed - whether debugging a Python integration, optimizing a Go service, or wiring up infrastructure automation.
• AI Enthusiast: You have already experimented with AI in your work or personal projects and are eager to find ways to use it to make your work smarter and more efficient.
• Extreme Ownership: You take pride in the end-to-end health of the platform and proactively advocate for engineering excellence.

Technologies we use (not exhaustive):

• Backend: Python, Django, FastAPI, Go
• Frontend: React, TypeScript
• Infrastructure and CI: AWS, Kubernetes, Terraform, Helm, Buildkite, Pants
• Data: MySQL, PostgreSQL, Redis, Kafka
• AI Tools: Claude, Cursor, Copilot, or internal AI enablement frameworks