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, Memcached, Apache Zookeeper, Apache Pulsar Cloud & DevOps: AWS (EC2, RDS, Aurora), Terraform, Jenkins Location & Work Model: This role is based in Dublin, Ireland and follows a hybrid working model. Klaviyo supports work authorization and relocation for this position. At Klaviyo, we enjoy tackling meaningful engineering challenges and value people who take ownership, learn continuously, and collaborate openly. We are committed to building inclusive teams and encourage applications from candidates of all backgrounds. Klaviyo is growing fast and we have openings for all skill levels across all of our teams. Learn more about our engineering culture at https://klaviyo.tech Our salary range reflects the cost of labour in the country where the job post is advertised. The base salary offered for this position is determined by several factors, including the applicant’s job-related skills, relevant experience, education or training, and work location. In addition to base salary, our total compensation package may include participation in the company’s annual cash bonus plan, variable compensation (OTE) for sales and customer success roles, equity, sign-on payments, and a comprehensive range of health, welfare, and wellbeing benefits based on eligibility.  Your recruiter can provide more details about the specific salary/OTE  range for your preferred location during the hiring process.Base Pay Range in Local Currency:€112.000—€168.000 EURThis role may require up to 10% travel for purposes such as new hire onboarding, client or partner work if applicable, team meetings, and industry events. Travel is coordinated in advance. Get to Know Klaviyo We’re Klaviyo (pronounced clay-vee-oh). We empower creators to own their destiny by making first-party data accessible and actionable like never before. We see limitless potential for the technology we’re developing to nurture personalized experiences in ecommerce and beyond. To reach our goals, we need our own crew of remarkable creators—ambitious and collaborati