Lead Software Engineer - Experimentation & Optimization

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 careers.klaviyo.com to see how we empower creators to own their own destiny.

Location: Boston, MA

Klaviyo operates a real-time data analytics platform, built primarily in Python and hosted on Amazon Web Services (AWS), scalable by design to meet increasing demand. Engineers at Klaviyo bring experience from diverse backgrounds and disciplines, contributing to a collaborative and high-impact environment.

The Experimentation & Optimization team is a full-stack engineering team that builds intuitive and robust experimentation solutions for Klaviyo users. We prioritize rigorous statistical methods and ensure model explainability, working closely with data scientists and UX designers to create a seamless user experience. Our team is responsible for developing and enhancing Klaviyo’s experimentation platform, enabling users to experiment with and optimize campaigns, flows, and forms to improve audience engagement. By providing a powerful platform, expert guidance, in-depth analysis, and actionable insights, we help businesses extract meaningful learnings from their data. Our work integrates deeply with Klaviyo’s core technologies, requiring close collaboration across the engineering organization to build scalable, data-driven solutions.

As a Lead Software Engineer on the Experiments Platform Team, you will play a key role in shaping the architecture and strategy for experimentation at Klaviyo. You’ll lead technical discussions on how to design and implement robust experimentation features that help users optimize their marketing efforts. You’ll own the team’s mission, goals, and roadmap, collaborating closely with technical product owners and managers to develop a cohesive strategy that aligns both technical and business objectives. Your work will directly impact Klaviyo’s customers by enabling them to make data-driven decisions that enhance engagement and business outcomes.

Our tech stack includes 

• Python, FastAPI, gRPC, TypeScript, React, AWS, Django, and Spark.
• MySQL, PostgreSQL, Clickhouse, Redis, DynamoDB
• AWS, Terraform, Docker, Argo

How You Will Make a Difference

• Lead the technical vision for experimentation and optimization at Klaviyo, shaping how we design, build, and scale our experimentation platform.
• Deliver key product capabilities in experimentation and optimization, enabling users to test and refine campaigns, flows, and forms to maximize engagement.
• Work with large-scale data volumes to build systems that provide actionable insights to businesses of all sizes, from small startups to enterprise customers.
• Design and implement scalable experimentation infrastructure that processes massive datasets efficiently.
• Research, test, and productionalize experimentation methodologies and algorithms that provide measurable improvements in user engagement.
• Become a subject matter expert (SME) in experimentation and optimization, helping to drive best practices across the organization.
• Work cross-functionally with product, design, and data science teams to create a seamless experimentation experience for Klaviyo users.
• Have ample opportunities for growth and impact, given the scope of this role and the team’s central role in Klaviyo’s product strategy.

Who You Are

• 10+ years of experience as a hands-on software engineer.
• Experience architecting and building intuitive, consistent APIs in either REST or GraphQL
• Passionate about creating systems that elegantly simplify complex patterns and practices
• Proven ability to lead the technical vision for a platform or product area, shaping architecture and strategy to drive impact.
• Successfully led and delivered complex, multi-quarter projects involving multiple teams.
• Motivated to grow the team, both by mentoring team members and attracting new talent to expand our capabilities.
• Excited to dive into the code, deeply understand the experimentation and optimization space, and provide applicable technical mentorship.
• Strong understanding of cloud architectures and scalable systems, knowing the right tools to use based on the problem at hand.

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.

The pay range for this role is listed below. Some sales and success roles are also eligible for variable compensation and hourly non-exempt roles are eligible for overtime in accordance with applicable law. This role is eligible for benefits, including: medical, dental and vision coverage, health savings accounts, flexible spending accounts, 401(k), flexible paid time off and company-paid holidays and a culture of learning that includes a learning allowance and access to a professional coaching service for all employees.

Base Pay Range For US Locations:$188,000—$282,000 USD

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.

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.

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