Lead Software Engineer, Messaging Infrastructure

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 system, responsible for delivering billions of messages, and must be architected for massive scale and reliability.

As a Lead Software Engineer in the Messaging Infrastructure organization, you'll provide technical leadership to a group of engineers building and scaling the services that power Klaviyo's messaging pipeline end-to-end. You'll drive technical strategy, own critical components of the delivery infrastructure, and help the team navigate the unique challenges of multi-channel compliance, regulatory requirements, provider integrations, and global deliverability. This is a hands-on technical leadership role where you'll contribute to architecture, code, and mentorship while shaping the future of messaging at Klaviyo.

How you will make a difference

Own and drive the architecture of key components in Klaviyo's messaging pipeline — from ingestion and routing through to delivery and status tracking

Lead a team of engineers building and scaling highly-available, high-throughput services across one or more messaging channels

Design and implement scalable backend services in Python and/or Go

Work on a campaign pipeline that processes and delivers hundreds of millions of messages daily, growing to billions-scale

Bring clarity to ambiguous technical problems — breaking undefined challenges into concrete, actionable plans

Collaborate across product, deliverability, compliance, and platform teams to expand messaging capabilities

Drive best practices in system design, code quality, and engineering process across your team

Mentor and grow engineers, contributing to a high bar across the broader Messaging Infra organization

Build smarter systems and workflows by putting AI at the center of how you and your team work

Who you are

8+ years of engineering experience with strong backend and distributed systems design skills

Proficient in Python and/or Go, and able to pick up the other quickly

Experienced with large-scale system architecture — familiar with the tradeoffs involved and able to apply them against real business constraints

Comfortable contributing to architecture and code directly; this is a hands-on role

Skilled in scaling infrastructure on AWS

Strong product and business mindset — you think beyond the code to understand customer impact

Self-directed and delivery-focused — you ship incremental value and iterate

Clear communicator who thrives in a high-autonomy, cross-functional environment

You've already experimented with AI in your work or personal projects and are excited to keep pushing on that

Technologies we use (not exhaustive)

Languages & Frameworks: Python, Django, React

Data & Infrastructure: MySQL, Redis, M