Technical Lead, Distributed Systems - Messaging

<div class="content-intro"><p><em>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 <a class="_ymio1r31 _ypr0glyw _zcxs1o36 _mizu194a _1ah3dkaa _ra3xnqa1 _128mdkaa _1cvmnqa1 _4davt94y _4bfu18uv _1hms8stv _ajmmnqa1 _vchhusvi _kqswh2mm _ect4ttxp _syaz13af _1a3b18uv _4fpr8stv _5goinqa1 _f8pj13af _9oik18uv _1bnxglyw _jf4cnqa1 _30l313af _1nrm18uv _c2waglyw _1iohnqa1 _9h8h12zz _10531ra0 _1ien1ra0 _n0fx1ra0 _1vhv17z1" href="http://klaviyo.com/careers" data-renderer-mark="true">klaviyo.com/careers</a> to see how we empower creators to own their own destiny.</em></p></div><p><strong>About Klaviyo</strong></p> <p>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.</p> <p><strong>About the Team</strong></p> <p>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 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.<br><br>As a <strong>Lead Software Engineer</strong> in the Messaging Infrastructure organization, you'll provide technical leadership to a group of engineers building and scaling the live, event-driven services that power Klaviyo's messaging pipeline end-to-end. You'll drive technical strategy for a system where every message is a real-time event with a customer's business outcome riding on it, 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.</p> <p><strong>How you will make a difference</strong></p> <ul> <li>Lead a team of engineers building and scaling highly-available, <strong>low-latency</strong>, <strong>high-throughput</strong> services across one or more messaging channels</li> <li>Own and drive the architecture of key components in Klaviyo's messaging pipeline — from ingestion and routing through to delivery and status tracking</li> <li>Design and implement scalable backend services in Python and/or Go, built to hold up under <strong>real-time</strong>, unpredictable load rather than scheduled batch windows</li> <li>Work on a campaign pipeline that processes and delivers hundreds of millions of messages daily, growing to billions-scale, with peak throughput measured in <strong>messages per second</strong> and performance tracked against<strong> p99 latency</strong>, not just daily volume</li> <li>Make real-time architectural tradeoffs on <strong>backpressure</strong>, delivery guarantees, and failure handling — decision