Senior Software Engineer, Data Science – Product Merchandising


  • Full Time

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.

The Klaviyo Data Science team loves programming and the excitement that comes with building something people use. We are the kind of people that love talking to users and can find the balance between solving a problem quickly and thinking about how code will scale in the future. We love to move fast, keep learning, and get stuff done.

Klaviyo operates a real-time data platform coded in Python built for massive scale on Amazon Web Services (AWS). Engineers come to Klaviyo with experience in a variety of languages and from a number of disciplines.

The Product Merchandising team provides ways to understand how your products are driving value and then put the right products in front of the right audiences. The team uses a variety of algorithmic techniques to extract insights from first party consumer behavior data, managing its own compute resources to analyze thousands of customers and serve hundreds of millions of recommendations each month. The team also partners with other internal teams to surface optimized product merchandising experiences across channels.

Technologies we use (not comprehensive!):

  • Python
  • Numpy, Scipy, Pandas
  • Aurora, Cassandra, Kafka
  • HTML, JavaScript, React
  • SageMaker

Klaviyo is growing fast and we have openings for all skill levels across all of our teams. Learn more about our engineering culture at and listen to our data science team podcast at

How you will make a difference:

  • Create features built on data science that thousands of our customers rely on daily to reach 100M+ of consumers to drive their business forward
  • Advance your technical skills in all facets ranging from front end web development and user experience to designing and building scalable services that power millions of emails every day.
  • Mentor talented junior engineers and set the example for code quality and software engineering excellence.
  • Work as a partner with the product team to scope work, write tech specs, prioritize features, and plan the roadmap.

Who You Are:

  • 3+ years of software engineering experience in a fast-paced SaaS environment
  • Enjoy working with new technologies ranging from the frontend to backend, and are particularly passionate and an expert in multiple stack areas
  • Passionate about working with Data Scientists in productizing data science / machine learning models for end-users, including building out the necessary back-end and UX/UI (Javascript / Typescript, React)
  • Deep knowledge of software engineering paradigms and design patterns, including hands-on experience developing in Python
  • Experience with database technologies such as SQL, PL/SQL and relational database schema design in production
  • Experience with developing test strategies, designing automation frameworks, writing unit/functional tests to drive up code coverage and automation metrics
  • Have a bachelor’s or advanced degree in computer science, applied math, statistics or other relevant quantitative discipline, or equivalent industry experience.

Get to Know Klaviyo

Klaviyo is a world-leading marketing automation platform dedicated to accelerating revenue and customer connection for online businesses. Klaviyo makes it easy to store, access, analyze and use transactional and behavioral data to power highly-targeted customer and prospect communications. The company's hybrid customer-data and marketing-platform model allows companies to grow by fostering direct relationships with customers, without giving up their valuable data to popular big-tech ad platforms. Over 265,000 innovative companies like Unilever, Custom Ink, Living Proof and Huckberry sell more with Klaviyo. Learn more at

Klaviyo is committed to diversity and to a policy of equal employment opportunity and non-discrimination. We do not discriminate on the basis of race, color, religion, national origin, age, sex, marital status, ancestry, physical or mental disability, veteran status, gender identity, sexual orientation or any other characteristic protected by applicable law.

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