Internship Math Software Engineer Jobs in Newton, MA

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What's it like to ship code that thousands of people actually use? As a Software Engineer at Klaviyo, you'll find out fast. We're builders here: we run toward problems, hold ourselves to a high bar, and believe the work itself is the reward. Another payoff of this early career role is growth. You'll sharpen your skills, learn from engineers who've been in the trenches, and get your hands on projects that matter from day one.

Our engineering teams build scalable, high-performance systems that power both our product and the infrastructure behind it. In this role, you'll get exposed to modern infrastructure and engineering practices that allow you to grow as a software engineer. We're an AI-first company, so you'll be expected to use AI tools to move faster, learn quicker, and do better work.

You'll have ownership: writing and testing code, documenting it, deploying it, and keeping it running in production. If you're ready to launch your engineering career building systems that matter in a fast-moving, product-driven environment, this is your role.

Dec 2026 grads: start dates on a rolling basis.
Spring 2027 grads: start dates June-August.

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

• Two previous internship/co-op roles working with production-level code
• Currently pursuing a degree in Computer Science, Engineering, Data Science, Math/Statistics, or a related field
• Graduating in December 2026 or May/June 2027
• 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 give and take feedback directly. Klaviyos pull problems closer instead of avoiding them.
• You're comfortable moving forward before every answer is known, and you adjust fast when the ground shifts under you.
• You embrace Klaviyo's "always learning" culture, continually pushing yourself to grow as an engineer.
• 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.

Engineering at Klaviyo

Our engineering teams are organized into pillars to keep the work focused. All Software Engineer I offers are team agnostic.  Team placement occurs ~ 30-day pre-start.  Placement can be on a full-stack, back-end, or front-end team within any of the pillars.

• 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.

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.