Senior Software Engineer - Channel Processing

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 klaviyo.com/careers to see how we empower creators to own their own destiny.

Why You Should Join the Channel Processing Team

The Channel Processing team has direct technical responsibility for Klaviyo’s most-used engagement product. It is responsible for designing, building and operating highly-scalable, highly-available distributed systems to process ever-increasing campaign traffic. Our systems are used by hundreds of thousands Klaviyo customers to schedule/process tens of thousands campaigns and deliver over 1B messages every day. Besides the daily high volume traffic, the more challenging task is to  deal with super spiky volume at online sale seasons. During the 2025 Black Friday and Cyber Monday, over 10B messages got processed and delivered through our system without any manual intervention. We’re proud of these achievements and passionate about continually scaling and evolving our systems to support and help drive Klaviyo’s rapid growth by using modern technologies and patterns.  Going beyond the established channels, this team is aiming to build a highly generic and extensible campaign platform to empower the new emerging message channels in future by leveraging our years of experience/expertise. If you like to take on new challenges working on large-scale, complex systems, come join us.

How You Will Make a Difference

• In this role, you will own and build features/services that hundreds of thousands of Klaviyo customers rely on daily to drive their business forward.
• Work on crafting our highly-scalable, highly-available campaign pipeline that processes and delivers hundreds of millions of messages daily growing to billions scale.
• Collaborate radically with teams and stakeholders across Klaviyo on designs, implementations, and engineering practices.
• Learn new technologies, bring them to the team and apply them to evolve our systems to the next level.
• Help us improve our experimentation and development processes, and mentor other engineers on the team.
• Participate in the technical interview process to help maintain a high bar for our growing teams
• Contribute to the company as a subject matter expert, constantly pushing yourself to be a better engineer and to level up all of your peers within your team and within Klaviyo.

Who You Are

• Have 4-6+ years of experience in a software engineering discipline and have architected, built and delivered at least one complex system.
• Experience on large-s