Senior Software Engineer - Developer… at Klaviyo · Boston

At Klaviyo, we value the unique backgrounds, experiences and perspectives each Klaviyo (we call ourselves Klaviyos) brings to our workplace each and every day. We believe everyone deserves a fair shot at success and appreciate the experiences each person brings beyond the traditional job requirements. If you’re a close but not exact match with the description, we hope you’ll still consider applying. Want to learn more about life at Klaviyo? Visit klaviyo.com/careers to see how we empower creators to own their own destiny. 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 Massachusetts Applicants: It is unlawful in Massachusetts to require or administer a lie detector test as a condition of employment or continued employment. An employer who violates this law shall be subject to criminal penalties and civil liability. Our salary range reflects the cost of labor across various U.S. geographic markets. The range displayed below reflects the minimum and maximum target salaries for the position across all our US locations. The base salary offered for this position is determined by several factors, including the applicant’s job-related skills, relevant experience, education or training, and work location. In addition to base salary, our total compensation package may include participation in the company’s annual cash bonus plan, variable compensation (OTE) for sales and customer success roles, equity, sign-on payments, and a comprehensive range of health, welfare, and wellbeing benefits based on eligibility. Your recruiter can provide more details about the specific salary/OTE range for your preferred location during the hiring process. Base Pay Range For US Locations: $148,000—$222,000 USD This role may require up to 10% travel for purposes such as new hire onboarding, client or partner work if applicable, team meetings, and industry events. Travel is coordinated in advance. Get to Know Klaviyo We’re Klaviyo (pronounced clay-vee-oh). We empower creators to own their destiny by making first-party data accessible and actionable like never before. We see limitless potential for the technology we’re developing to nurture personalized experiences in ecommerce and beyond. To reach our goals, we need our own crew of remarkable creators—ambitious and collaborative teammates who stay focused on our north star: delighting our customers. If you’re ready to do the best work of your career, where you’ll be welcomed as your whole self from day one and supported with generous benefits, we hope you’ll join us. AI fluency at Klaviyo includes responsible use of AI (including privacy, security, bias awareness, and human-in-the-loop). We provide accommodations as needed. By participating in Klaviyo’s interview process, you acknowledge that you have read, understood, and will adhere to our Guidelines for using AI in the Klaviyo interview Process. For more information about how we process your personal data, see our Job Applicant Privacy Notice. Klaviyo is committed to a policy of equal opportunity and non-discrimination. We do not discriminate on the basis of race, ethnicity, citizenship, national origin, color, religion or religious creed, age, sex (including pregnancy), gender identity, sexual orientation, physical or mental disability, veteran or active military status, marital status, criminal record, genetics, retaliation, sexual harassment or any other characteristic protected by applicable law. IMPORTANT NOTICE: Our company takes the security and privacy of job applicants very seriously. We will never ask for payment, bank details, or personal financial information as part of the application process. All our legitimate job postings can be found on our official career site. Please be cautious of job offers that come from non-company email addresses (@klaviyo.com), instant messaging platforms, or unsolicited calls. By clicking "Submit Application" you consent to Klaviyo processing your Personal Data in accordance with our Job Applicant Privacy Notice.  If you do not wish for Klaviyo to process your Personal Data, please do not submit an application.You can find our Job Applicant Privacy Notice here and here (FR).