Sr. Lead Software Engineer - Messaging Infrastructure

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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 Senior Lead Software Engineer within the Messaging Infra organization, you will serve as the primary technical architect for our high-volume message delivery systems while driving the overarching technical vision for channel expansion. You will partner with leaders across all channels to ensure a scalable, reliable, and performant platform strategy, acting as a key technical liaison to the broader Mobile Channels and Messaging Infrastructure pillar. Your leadership will ensure that our core systems are not just maintained, but architected to accelerate innovation and business impact while raising the bar on scalability and reliability.

What You'll Do

As a Senior Lead Software Engineer, you will have an overarching responsibility for the architecture, health, and scaling of the Messaging Infra platform with a focus on high-volume message delivery. Your role will involve:

• Technical Strategy: Define the technical strategy and architectural vision for the Messaging Infra platform, ensuring all system improvements align with long-term business goals for massive scalability, high reliability, and low latency message delivery.
• System Architecture and Improvement: Serve as the primary architect to build and improve high-volume message delivery systems across multiple channels, focusing on throughput, performance, and reliability.
• Cohesive Technical Vision: Drive technical leadership to guide architectural decisions across multiple teams, striving towards a cohesive technical vision across multiple roadmap items and providing solutions for complex problems around scalability and performance.
• Platform Rollouts and Product Execution: Oversee and execute the planning and seamless rollout of major software releases and updates for the platform, managing the entire lifecycle from design to deployment in production environments including significant individual contributions.
• Problem Solving and Reliability: Act as a go-to expert for diagnosing and resolving complex performance, scalability, and reliability issues across the messaging platform. Implement proactive monitoring and telemetry to identify and address problems before they become critical incidents.
• Mentorship: Mentor other engineers regularly, primarily experienced lead and senior engineers, to develop new technical leadership for the company.
• Cross-functional Collaboration: Partner with product managers, deliverability and compliance specialists, and other stakeholders to gather requirements, resolve conflicts, and ensure alignment across all teams and projects.
• Continuous Improvement: Stay current with emerging technologies and industry trends, evaluating new tools and practices to identify how they can improve systems and internal processes.

Who You Are

• 12 years of experience in software development, strong knowledge of computer science fundamentals, domain-driven design, and extensive expertise in architectural patterns, specifically within the domain of distributed systems.
• Have proven that you can build and scale complex distributed systems, including solving problems in sustainable ways, balancing pragmatic development with ideal architecture, breaking through technical obstacles with vigor, and leading teams through crises by working side by side with them in the trenches.
• BA or BS Degree in Computer Science, related field, or equivalent experience.
• Technical Expertise: Deep expertise in relevant programming languages (e.g., Python, Go) and cloud platforms (AWS, Azure, GCP), containerization (Kubernetes, Docker), and Infrastructure as Code (Terraform). You are particularly passionate and an expert in multiple stack areas, with strong and opinionated experience with various technologies, and know how to pick the right tool for any job.
• Technical Strategy: Demonstrated experience in contributing to the product and platform vision, as well as defining the strategy within the broader scope of long-term organizational needs.
• Architectural Skills: Strong understanding of software architecture, design patterns, and system integration, with the ability to define technical strategies and influence architectural decisions across multiple teams.
• Soft Skills: Exceptional problem-solving, analytical, leadership, and communication skills, with the ability to articulate complex technical concepts to both technical and non-technical audiences.
• AI Enthusiast: You’ve already experimented with AI in work or personal projects, and you’re excited to dive in and learn fast. You’re hungry to responsibly explore new AI tools and workflows, finding ways to make your work smarter and more efficiently.

Nice to Have

• Experience with the email and/or SMS ecosystem, including understanding of channel-specific protocols and security specifications (e.g., DKIM, DMARC, SPF), and familiarity with key 3rd-party entities (like mailbox providers, anti-abuse groups, and telecoms) and compliance rules/best practices.
• Background in performance optimization and a passion for digging into performance and scalability issues to drive breakthrough solutions.
• Familiarity with complex data management for testing, including large datasets and production-like data replication.

Our Tech Stack

• Python, Django, FastAPI, Celery
• Apache Kafka, Apache Pulsar, RabbitMQ, Spark, Airflow, and other tech from the big data stack
• MySQL, PostgreSQL, Clickhouse, Cassandra, Redis
• Typescript, React, Backbone.js, HTML, JavaScript, Babel, Jest, Webpack
• Graphite, statsd, Chronosphere
• AWS (EC2, RDS, Aurora, etc.), Terraform, Docker, Kubernetes (EKS), Pantsbuild, Argo, and other modern DevOps tools

We use Covey as part of our hiring and / or promotional process. For jobs or candidates in NYC, certain features may qualify it as an AEDT. As part of the evaluation process we provide Covey with job requirements and candidate submitted applications. We began usingCovey Scout for Inbound on April 3, 2025.

Please see the independent bias audit report covering our use of Coveyhere

Massachusetts Applicants:It is unlawful in Massachusetts to require or administer a lie detector test as a condition of employment or continued employment. An employer who violates this law shall be subject to criminal penalties and civil liability.

Our salary range reflects the cost of labor across various U.S. geographic markets. The range displayed below reflects the minimum and maximum target salaries for the position across all our US locations. 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 For US Locations:

$216,000—$324,000 USD

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 Noticehere and here (FR).