Technical Lead, 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 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.

As a Lead Software Engineer 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.

How you will make a difference

• Lead a team of engineers building and scaling highly-available, low-latency, high-throughput services across one or more messaging channels
• Own and drive the architecture of key components in Klaviyo's messaging pipeline — from ingestion and routing through to delivery and status tracking
• Design and implement scalable backend services in Python and/or Go, built to hold up under real-time, unpredictable load rather than scheduled batch windows
• Work on a campaign pipeline that processes and delivers hundreds of millions of messages daily, growing to billions-scale, with peak throughput measured in messages per second and performance tracked against p99 latency, not just daily volume
• Make real-time architectural tradeoffs on backpressure, delivery guarantees, and failure handling — decisions that affect whether a message goes out now
• 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 building and operating online, real-time distributed systems — systems processing live events where latency and timely processing matter to the customer or downstream service, rather than primarily offline/batch pipelines where processing can be deferred and replayed without immediate customer impact
• You've owned production services measured in messages/events per second, not just daily or monthly totals, and can speak concretely to p95/p99 latency under real, unpredictable traffic
• You've built with streaming or message-queue platforms (Kafka, Pulsar, RabbitMQ, SQS, or similar) as a core part of a system's design, and can talk through the tradeoffs of the ones you've used
• Experienced architecting distributed, event-driven systems at scale — familiar with the tradeoffs involved in keeping a live, high-throughput pipeline reliable, and able to apply them against real business constraints
• Proficient in Python and/or Go, and able to pick up the other quickly
• Skilled in scaling infrastructure on AWS for systems that must stay available and low-latency under spiky, unpredictable load
• Comfortable contributing to architecture and code directly; this is a hands-on role
• 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 EUR

This 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 collaborative teammates who stay focused on our north star: delighting our customers. If you’re ready to do the best work of your career, where you’ll be welcomed as your whole self from day one and supported with generous benefits, we hope you’ll join us.

AI fluency at Klaviyo includes responsible use of AI (including privacy, security, bias awareness, and human-in-the-loop). We provide accommodations as needed. 

By participating in Klaviyo’s interview process, you acknowledge that you have read, understood, and will adhere to our Guidelines for using AI in the Klaviyo interview Process. For more information about how we process your personal data, see our Job Applicant Privacy Notice.

Klaviyo is committed to a policy of equal opportunity and non-discrimination. We do not discriminate on the basis of race, ethnicity, citizenship, national origin, color, religion or religious creed, age, sex (including pregnancy), gender identity, sexual orientation, physical or mental disability, veteran or active military status, marital status, criminal record, genetics, retaliation, sexual harassment or any other characteristic protected by applicable law.

IMPORTANT NOTICE: Our company takes the security and privacy of job applicants very seriously. We will never ask for payment, bank details, or personal financial information as part of the application process. All our legitimate job postings can be found on our official career site. Please be cautious of job offers that come from non-company email addresses (@klaviyo.com), instant messaging platforms, or unsolicited calls.   By clicking "Submit Application" you consent to Klaviyo processing your Personal Data in accordance with our Job Applicant Privacy Notice.  If you do not wish for Klaviyo to process your Personal Data, please do not submit an application.  You can find our Job Applicant Privacy Notice here and here (FR).