Software Engineer Co-op

At Klaviyo, our Engineering teams build scalable, high-performance systems that power both our product and the infrastructure behind it.  As a Software Engineering Co-op, you'll be part of a fast-paced, collaborative team whose work reaches thousands of customers worldwide. You won't just be writing code. You'll be solving hard problems, shaping how users experience our product, and learning from engineers who've been doing this for a while.

This co-op is your shot to put your software development skills to work in production. You'll be embedded on one of our engineering teams (see overviews below), take on projects that matter to our customers, and build a technical foundation as you make connections across the business.

Our co-ops come from all kinds of coding backgrounds, but they all share one thing: they're excited to build, own, and scale features end-to-end, from scratch. You'll work alongside experienced engineers, take on hard technical problems, and ship code that supports Klaviyo's mission. We're an AI-first company, so you'll be expected to use AI tools to support your work, learn faster, and do your best work here.

How you'll make an impact

• Own features that our 180K+ paying customers rely on daily to reach their consumers and grow their business.

• Take responsibility for the mission, technical direction, and operation of projects with immediate impact.

• Own the full lifecycle of your code: writing it, testing it, shipping it, and making it better over time. Ownership is expected here, not just encouraged.

• Build and ship features that meet a high bar and grow your technical skills while you do it.

• Get hands-on debugging real issues, both locally and in production.

• Contribute to documentation and support your team during incidents (real-world problems teach you things a tutorial never will).

• Work closely with your teammates: ask questions, share ideas, and get better by taking feedback seriously.

• Learn to use the right tool for the job, lean into AI, and keep looking for ways to make things better.

• Put AI at the center of how you work to move faster. Build smarter systems and better workflows from the ground up.

Who you are

• At least one previous software engineering internship or co-op, with hands-on software development experience

• Currently pursuing a degree in Computer Science, Engineering, Data Science, Math/Statistics, or a related field

• Graduating in December 2027 or May/June 2028

• Experience with some of these technologies and languages:

  • Python, Django, Typescript, React, Go

  • MySQL, Cassandra, Clickhouse, Kafka, Redis

  • Amazon Web Services (EC2, RDS, Aurora, etc.), Terraform

• You enjoy working across new technologies and you’re excited  to work across the stack from back-end to front-end work

• You love digging into performance and scalability issues to find breakthrough solutions: a slow-loading UI, too many clicks in a workflow, a database query timing out, a queue that won't drain. You believe every problem can be solved, and you'd rather run toward it than around it.

• You enjoy shipping code early and often, working closely with products to build better software based on feedback from thousands of end users.

• You embrace Klaviyo's "always learning" culture. We learn faster together, which is part of why this program happens in person.

• You've already experimented with AI in work or personal projects, and you're excited to find ways to make your work smarter and more efficient.

Co-op logistics

• Our Spring Co-op Program is a paid experience [January 4–June 25] at our Boston, MA headquarters. Co-ops are in office 5 days a week.

• Offers will be team agnostic.  Co-ops are placed on a team approximately 30 days from the start of the program. Team placement can be on a full-stack, back-end, or front-end team within any of the pillars.

• Before joining individual teams, all co-ops go through Klaviyo Base Camp, our onboarding experience built to get you up to speed on Klaviyo, our product, and the day-to-day of engineering here.

• Our Boston office is genuinely fun. Lunch is on us 5 days a week, along with free snacks and drinks, ping pong, Nintendo Switch, a golf simulator, and a speakeasy to unwind in.

• Throughout the program, co-ops get together for social events beyond team and project work: a Red Sox game, trips to Versus and Activate, ice cream socials, and Ask Me Anything sessions with Klaviyo's senior leadership.

• Apply before October 7 if you can. We interview and hire on a rolling basis.

Former co-op projects

• Redesigned and refactored the email editor component architecture for performance and scalability, including reusable shared components and testing coverage improvements.

• Developed and deployed a new invite management microservice handling multiple roles, statuses, and integrations with audit logs.

• Built a real-time data ingestion and aggregation pipeline using kinesis and redshift, with monitoring and validation.

• Designed and implemented an automated rollback system that detects new unhandled sentry errors and notifies deployers via Slack.

• Own the WhatsApp double opt-in (DOI) feature end-to-end, integrating backend validation, frontend UI, and monitoring dashboards.

• Integrated AI-assisted tools into build validation pipelines, measuring productivity impact and creating internal best practices guide.

Engineering at Klaviyo

Our engineering teams are organized into pillars to keep the work focused.

• Data Infrastructure: Empower our internal teams and customers to get the best out of our data and agent platforms. underlying capabilities: Agent Platform, CDP revenue, Data Lake usage, Active API endpoints, Accounts with healthy API usage

• MCMI: Own the growth, revenue, and reliability of our mobile channels and all messaging infrastructure.

• Core Infrastructure: Empower our internal engineering, sales, and service teams to be as effective as possible by improving productivity of the eng, product, and design teams.

• Growth Marketing Platform: Give marketers the tools they need to engage with their customers, be successful, and know where they stand.

• AI & Analytics: Applies AI, data, and analytics to automate work, surface insights, and help customers make smarter decisions that maximize Klaviyo Attributed Value (KAV).

• Autonomous Service: Builds AI-powered customer service experiences that help resolve issues, support transactions, and connect customers with human assistance when needed.

• Product Security: Engineer the proactive defenses, detection systems, and response tooling that safeguard Klaviyo's customers and their data.

If you're excited about this role but your background doesn't check every box, apply anyway. Some of the strongest Klaviyos didn't start with a perfect resume match.

This role is not eligible for immigration sponsorship.

Equal Employment Opportunity and Diversity Statement

We are committed to equal employment opportunity in both principle and as a matter of policy. We will recruit, hire, train, promote, compensate and provide benefits to all applicants and employees without regard to ancestry, sex, race, color, ethnicity, national origin, gender, age, religion, religious creed, mental and/or physical disability, medical condition, military and/or veteran’s status, genetic information, marital status, sexual orientation, gender identity and/or expression, or any other basis protected by applicable federal, state and local laws. This policy applies to all recruiting, hiring, promotions, upgrades, layoffs, compensation, benefits, terminations and all other privileges, terms and conditions of employment. The firm complies fully with all federal, state and local equal employment opportunity laws.