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Senior 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.

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. 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. We prioritize rigorous statistical methods and ensure model explainability, working closely with data scientists and UX designers to create a seamless user experience. 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.

We are looking for a Senior Software Engineer to design and build experimentation features that empower Klaviyo customers to make data-driven decisions. You’ll play a critical role in technical discussions around how we architect scalable and statistically rigorous systems. You’ll own key projects that contribute to the team’s mission and roadmap, working closely with product managers, analysts, and other engineers to deliver impactful solutions. Your work will directly influence how customers test and optimize their marketing strategies.

 

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

  • Build and deliver experimentation and optimization capabilities that help Klaviyo users test and improve their marketing strategies.
  • Design and implement scalable systems that support a wide range of experiment types across campaigns, flows, and forms.
  • Contribute to the evolution of Klaviyo’s experimentation infrastructure, working with large-scale data to deliver meaningful insights for businesses of all sizes.
  • Collaborate cross-functionally with product, design, and data science to create a seamless and statistically rigorous experimentation experience.
  • Grow your expertise in experimentation methodologies and help influence best practices across teams.

 

Who You Are

  • 5+ years of experience as a full stack engineer, preferably within a SaaS product environment.
  • Experience developing intuitive, consistent APIs in either REST or GraphQL
  • Strong understanding of scalable web and data architectures, with experience designing or building experimentation or optimization features.
  • Demonstrated success delivering complex projects that span multiple sprints or quarters.
  • Familiarity with experimentation platforms, statistical analysis, or MLOps practices.
  • Curious, impact-driven, and excited to dive into challenging technical domains to help shape core product capabilities.
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:
$152,000$228,000 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.

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.
 
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Average salary estimate

$190000 / YEARLY (est.)
min
max
$152000K
$228000K

If an employer mentions a salary or salary range on their job, we display it as an "Employer Estimate". If a job has no salary data, Rise displays an estimate if available.

What You Should Know About Senior Software Engineer, Experimentation & Optimization, Klaviyo

Join Klaviyo as a Senior Software Engineer in Experimentation & Optimization and dive into an exciting opportunity to shape the future of marketing technology! At Klaviyo, we foster a culture of inclusivity and collaboration, valuing the distinct experiences each Klaviyo (we like to call ourselves) brings to the table. As part of our full-stack engineering team, you'll contribute to building a robust experimentation platform that empowers our users to optimize their campaigns, flows, and forms. Your primary focus will be on designing and implementing features that enable data-driven decision-making, ensuring our users can improve audience engagement effectively. You'll collaborate closely with product managers, data scientists, and UX designers to create an intuitive and seamless user experience, while also engaging in technical discussions to architect scalable systems using our diverse tech stack that includes Python, FastAPI, TypeScript, and AWS. If you have over five years of experience, particularly in a SaaS environment, and are passionate about experimentation methodologies, we would love for you to help us enhance our experimentation capabilities. Your contributions will directly impact how our clients drive their engagement strategies. If you're excited about making a meaningful difference and working in a supportive environment where your unique perspective is valued, we encourage you to consider becoming part of our team here at Klaviyo.

Frequently Asked Questions (FAQs) for Senior Software Engineer, Experimentation & Optimization Role at Klaviyo
What are the responsibilities of a Senior Software Engineer, Experimentation & Optimization at Klaviyo?

As a Senior Software Engineer in Experimentation & Optimization at Klaviyo, your responsibilities will include designing and building experimentation features that empower our customers to test and enhance their marketing strategies. You'll collaborate with cross-functional teams to create scalable systems that support various experiment types, contributing to Klaviyo's experimentation infrastructure and ensuring it scales effectively with data requirements.

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What qualifications do I need to apply for the Senior Software Engineer position at Klaviyo?

To qualify for the Senior Software Engineer position in Experimentation & Optimization at Klaviyo, candidates should have a minimum of five years of experience as a full-stack engineer in a SaaS environment. Proficiency in developing APIs (REST or GraphQL) and a solid understanding of scalable web architectures and experimentation frameworks are essential for this role.

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How does the Experimentation & Optimization team at Klaviyo collaborate with other teams?

The Experimentation & Optimization team at Klaviyo works closely with product managers, UX designers, and data scientists to create a cohesive and user-friendly experimentation experience. This collaboration ensures that the features developed provide meaningful insights while adhering to rigorous statistical methods, ultimately enhancing customer engagement and satisfaction.

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What technologies does Klaviyo use for the Senior Software Engineer position?

In the Senior Software Engineer role for Experimentation & Optimization at Klaviyo, you'll be working with a tech stack that includes Python, FastAPI, TypeScript, React, AWS, Django, and Spark. You'll also engage with databases like MySQL, PostgreSQL, Clickhouse, Redis, and DynamoDB, using tools such as Terraform, Docker, and Argo in your development process.

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Is there room for career growth as a Senior Software Engineer at Klaviyo?

Absolutely! At Klaviyo, we believe in fostering talent and providing our employees with opportunities to grow. As a Senior Software Engineer in Experimentation & Optimization, you'll have the chance to expand your skill set, engage in leadership discussions, and contribute to strategic projects that influence key outcomes within the company.

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Common Interview Questions for Senior Software Engineer, Experimentation & Optimization
Can you explain your experience with building scalable experimentation systems?

When answering this question, you should emphasize specific projects where you've designed systems that can handle increasing loads and data requirements. Highlight any relevant technical methodologies you used and the outcome, showing your ability to create systems that grow with demand.

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What are some best practices you follow for API design?

Discuss your approach to API design, including principles like RESTful design, versioning, and maintaining backward compatibility. Provide examples of APIs you've developed, and elaborate on how these practices improved usability and integration experience for clients.

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How do you prioritize features when working on a cross-functional team?

To answer this question, provide insight into your collaboration process, focusing on how you gather input from product managers, data scientists, and other stakeholders. Mention any prioritization frameworks you use, like MoSCoW, that help ensure alignment with business goals and user needs.

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Describe a challenge you've faced while working on an experiment and how you overcame it.

Use the STAR method (Situation, Task, Action, Result) to frame your answer. Detail a specific challenge related to experimentation, explain the steps you took to address it, and share the positive outcome that resulted from your efforts.

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How do you ensure statistical rigor in your experimentation strategies?

Bring up various statistical methods and frameworks that you incorporate into your experimentation process, such as A/B testing principles, sample size calculations, or hypothesis testing. Discuss how these practices lead to valid, reliable insights that inform data-driven decisions.

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Have you worked with any experimentation platforms, and if so, which ones?

Mention any specific experimentation platforms you've used, highlighting your experience configuring, analyzing, and deriving insights from the data generated. Provide concrete examples of how those experiences informed your approach to experimentation.

Join Rise to see the full answer
What is your experience with Agile methodologies and how have they affected your work?

Discuss how Agile principles have shaped your approach to software development, mentioning specific methodologies like Scrum or Kanban that you've applied in past projects. Explain how Agile promotes flexibility, collaboration, and timely delivery of features.

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What steps do you take to ensure high code quality?

Emphasize practices like code reviews, unit testing, and continuous integration/deployment that you implement to maintain high standards. Provide specific examples of how these practices contributed to project success.

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How do you handle tight project deadlines while maintaining quality?

Discuss strategies you use when managing tight deadlines, such as breaking down tasks, setting realistic timelines, and prioritizing critical features. Highlight how you maintain communication with your team to ensure everyone is aligned and focused on delivering the project successfully.

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What are your long-term goals as a Senior Software Engineer?

Share your aspirations that align with the company's mission and growth. Express a desire to continue developing your skills in experimentation and optimization technologies while contributing to team leadership and mentorship opportunities at Klaviyo, demonstrating your commitment to personal and professional growth.

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Klaviyo is a global technology company committed to providing a marketing automation platform, used primarily for email marketing and SMS marketing by approximately 143,000 e-commerce merchants.

304 jobs
MATCH
VIEW MATCH
BADGES
Badge Flexible CultureBadge Global CitizenBadge InnovatorBadge Future Unicorn
CULTURE VALUES
Inclusive & Diverse
Diversity of Opinions
Transparent & Candid
Growth & Learning
Customer-Centric
Mission Driven
Rapid Growth
Work/Life Harmony
FUNDING
SENIORITY LEVEL REQUIREMENT
TEAM SIZE
EMPLOYMENT TYPE
Full-time, on-site
DATE POSTED
March 28, 2025

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