Senior Software Engineer, Distributed Systems - Messaging

Klaviyo; Dublin; Hybrid; EUR 92,000 - 138,000; Full time

Job summary

Klaviyo is a leading marketing automation platform in Dublin, Ireland, seeking engineers to build and operate real-time distributed systems and event-driven backends. You will work on a high-volume messaging pipeline, ensuring low latency and high throughput across multiple channels.

The role emphasizes ownership, collaboration, and mentorship, with a focus on performance, scalability, and data-driven decision making within a hybrid work model in Dublin.

Qualifications

• 5+ years of professional software engineering experience building and operating online, real-time distributed systems.
• Experience designing and building event-driven or asynchronous systems with queues, streams or messaging platforms.
• Experience with streaming or message-queue platforms such as Kafka, Pulsar, RabbitMQ, SQS, or similar.
• Strong background in large-scale system architecture and patterns.
• Fluency in at least one backend language (Python, Go, Java, Scala) and navigating large codebases.
• Interest in performance and scalability improvements and data-driven decision making.

Responsibilities

• Build and scale highly-available, low-latency, high-throughput, event-driven services for live messaging across channels.
• Work on real-time messaging pipeline processing hundreds of millions of messages daily.
• Design and implement backend services handling real-time traffic, queues and streams with tradeoffs on throughput and reliability.
• Own components of a scalable campaign pipeline from processing to delivery and status tracking.
• Collaborate with teams on designs, implementations, and engineering practices.
• Learn new technologies and apply them to advance systems to the next level.
• Contribute to improved development processes and mentor other engineers.

Skills

Real-time systems

Event-driven

Streaming queues

Backend languages

Performance optimization

Mentoring

Distributed systems

Ownership

Tools

Kafka

Pulsar

RabbitMQ

SQS

AWS

Terraform

Jenkins

Job description

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 drain. You recognize all problems can be solved.
• Passionate about growing and improving a product daily using a data driven mindset, familiar with system monitoring and alerting techniques.
• Proven experience with being a coach and a mentor for team members and helping them grow.
• Solid understanding of distributed systems fundamentals: consistency models, CAP, tradeoffs, idempotency, retries and backoff, rate limiting, and graceful degradation.
• Ability to operate effectively in a high-ownership culture: you drive your work forward, unblock yourself, and hold yourself accountable to outcomes, not just effort.

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 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: €92.000 — €138.000 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.