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

About Klaviyo

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.

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 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.

How You’ll Make an Impact

• 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.

What We’re Looking For

• 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
  • MySQL, Cassandra, Clickhouse, Kafka, Redis
  • Amazon Web Services (EC2, RDS, Aurora, etc.) Terraform
• 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.

Co-op Logistics

• 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 provides focused time to learn about Klaviyo, our product, the ins and outs of engineering.This robust training experience ensures all co-ops join their teams fully prepared to dive into project work and make an immediate impact.
• Our Boston office is fun! Our co-ops stay fueled with free snacks and drinks, take breaks over a game of ping pong, Nintendo Switch, or a round of golf in our golf simulator, and relax in our speakeasy.
• Throughout the program, Klaviyo co-ops attend social events to promote interaction beyond team and project work. In past years these events have included a Red Sox game, outings to Versus and Flight Club in the Boston Seaport, ice cream socials, and Ask Me Anything sessions with Klaviyo senior leadership.
• It is highly recommended that you apply prior to February 15th as we interview and hire on a rolling basis.

Engineering at Klaviyo

At Klaviyo our engineering teams are broken into pillars to streamline the work.

• Growth: Reduce friction across the board for our customers, increase cross-sells, and help us launch into new geographies and verticals
• Marketing Platform: Give marketers the tools they need to engage with their customers, be successful, and know where they stand
• Mobile Channels and Messaging Infrastructure: Own the growth of our mobile channels and all messaging infrastructure
• Data Infrastructure: Empower our internal teams and customers to get the best out of our data and underlying capabilities
• Core Infrastructure: Empower our internal engineering, sales, and service teams to be as effective as possible

This role is not eligible for immigration sponsorship.

We use Covey as part of our hiring and / or promotional process. For jobs or candidates in NYC, certain features may qualify it as an AEDT. As part of the evaluation process we provide Covey with job requirements and candidate submitted applications. We began using Covey Scout for Inbound on April 3, 2025.

Please see the independent bias audit report covering our use of Covey here

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 action.