Full-stack Software Engineer Co-op; Fall

Full-stack Software Engineer Co-op (Fall 2026)

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 an exact match with the description, we hope you’ll still consider applying.

About our Co-op

At Klaviyo, our Engineering team builds the foundational technologies that power how brands grow through owned marketing. As a Full-stack Software Engineering Co-op, you’ll be part of a fast-paced, collaborative environment where your work directly impacts thousands of customers worldwide. You won’t just be writing code—you’ll be solving real problems, shaping user experiences, and learning from seasoned engineers across our engineering organization.

This co-op is an opportunity to apply your software development skills in a production environment. You’ll be embedded within one of our engineering teams (see overviews below) and work on meaningful projects that make a real difference to our customers, all while building a strong technical foundation and connections across Klaviyo.

Co-ops come to Klaviyo with experience in a variety of coding languages, but they are all passionate about building, owning, and scaling features end-to-end from scratch. You ll work alongside seasoned engineers, break through complex technical challenges, and gain hands-on experience contributing to real products that support Klaviyo s mission. We operate a real-time data platform coded in Python built for massive scale on Amazon Web Services (AWS).

As an AI-first company you will be encouraged to use AI tools to support your work, accelerate learning, and succeed in your role.

• Own features that our 150K+ paying customers rely on daily to reach their consumers to drive their business forward
• Be responsible for the mission, technical direction and operations of projects that have immediate impact
• Architect and design robust and high performance data processing and storage systems leveraging new databases to serve different internal and external use cases
• Craft our highly scalable real-time data pipeline that processes billions of events weekly across data sets growing to petabyte scale
• Work on a deep analytics system that provides insight into hundreds of terabytes of data
• Transform workflows by putting AI at the center, building smarter systems and ways of working from the ground up.

• At least one previous software engineering internship/co-op with software development experience
• Currently pursuing a degree in Computer Science, Engineering, Data Science, Math/Statistics or related field
• Graduating in December 2026 or May/June 2027
• Experience with some of these technologies and languages:
• Python, Django, Typescript, React
• Enjoy working with new technologies ranging from the frontend to backend and adept at selecting the right tool for the job
• Love digging into performance and scalability issues to drive breakthrough solutions-- whether it s a slow loading UI or too many clicks in a workflow, a database query timing out, or a queue that just won’t drain. You recognize all problems can be solved.
• Enjoy shipping code early and often in an agile fashion, pairing with product management to craft better software by soliciting feedback from thousands of end-users
• Embrace Klaviyo’s “always learning” culture that fosters learning at every level, constantly pushing yourself to be a better engineer
• You’ve already experimented with AI in work or personal projects, and you’re excited to dive in and learn fast. You’re hungry to responsibly explore new AI tools and workflows, finding ways to make your work smarter and more efficient.

• Our Fall Co-op Program is paid experience [July 6th - December 18th] at our Boston, MA headquarters. Co-ops are required to be in the office 5 days a week.
• Before diving into individual teams and projects, all co-ops will complete Klaviyo Base Camp - our customized onboarding experience. Base Camp…