Senior Software Engineer, Distributed Systems - Messaging

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.

About Klaviyo

Klaviyo is a leading marketing automation platform that helps businesses grow by delivering personalized experiences. Our mission is to empower creators to own their destiny. We believe in providing an exceptional developer experience that enables our engineering teams to build and ship high-quality software efficiently and with confidence.

About the Team

The Messaging Infra organization at Klaviyo is focused on high-growth customer engagement through various messaging channels (email, SMS/MMS/RCS, mobile push, WhatsApp, and more). We work with multiple stakeholders to provide best-in-class service and reliability to connect a wide range of businesses, from entrepreneurs to enterprises, with their end users. The messaging platform is a mission-critical, event-driven system responsible for delivering billions of real-time, low-latency messages, and must be architected for massive scale and reliability.

How You Will Make a Difference

Build and scale highly-available, low-latency, high-throughput, event-driven services that process live messaging events across one or more channels.

Work on Klaviyo's real-time messaging pipeline, processing and delivering hundreds of millions of messages daily and growing to billions scale, with performance and reliability critical to whether messages reach customers when expected.

Design and implement backend services that handle real-time traffic, asynchronous processing, queues and streams, making tradeoffs around throughput, latency, reliability and failure handling.

Own and evolve components of a highly-scalable, highly-available campaign pipeline, from processing and routing through to delivery and status tracking.

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

5+ years of professional software engineering experience building and operating online, real-time distributed systems where latency, throughput and reliable processing matter to customers or downstream services.

Experience designing and building event-driven or asynchronous systems, using events, queues, streams or messaging platforms as a core part of the architecture.

Experience with streaming or message-queue platforms such as Kafka, Pulsar, RabbitMQ, SQS, or similar, and an understanding of the tradeoffs they introduce around throughput, latency, ordering, retries and reliability.

Experience with large-scale system architecture, technologies and patterns. Have a good understanding of their pros/cons and use scenarios, able to apply them to system design by making appropriate tradeoffs to meet business needs.

Deep fluency in at least one backend language (Python, Go, Java, Scala, or similar) and comfort navigating large, complex codebases.

Love digging into performance and scalability issues to drive breakthrough solutions -- whether it's a performance degradation, a database query timing out, or a queue that just won’t dra