Senior Software Engineer - Growth

Why You Should Join the Onboarding Team

The [Product Expansion / Activation] team at Klaviyo is focused on improving the early experience of Klaviyo for new customers. We work diligently to improve the rate at which customers are successfully setting up their Klaviyo account and gaining value from the platform. Engineers on the team use data to discover opportunities for improvement, implement A/B tests to validate ideas, and work across the product to iteratively improve UX and reduce friction for new customers.

How You Will Make a Difference

• Drive the technical design and lead the implementation of high-impact user-experience improvements across the Klaviyo product, focusing on areas critical to new customer success and adoption. Own the entire project lifecycle.
• Own the end-to-end experimentation process, including contributing to strategy, architecting and implementing A/B tests to validate hypotheses, and interpreting data to drive iterative improvements.
• Serve as a technical leader and liaison, collaborating across teams to define and prioritize key technical initiatives.
• Mentor and provide technical guidance to other engineers on the team, elevating experimentation, development, and operational practices.
• Define the architectural approach and technical strategy for your area of responsibility, anticipating scalability and reliability needs, including leveraging AI agents.
• Work from our Boston HQ 5 times per week.

Who You Are

• Extensive background in full stack software engineering, demonstrating deep understanding of systems and the ability to architect, deliver, and maintain software for high-scale, user-facing features, supporting APIs, and infrastructure.
• Demonstrated ability to drive technical strategy and improvement using a data-driven mindset.
• Demonstrated technical experience in using and championing AI-driven software delivery practices and methods.
• Experience driving A/B testing strategies for products with metric-based goals is a strong plus.
• Thrives in an entrepreneurial-type environment that is customer-focused and strategic.