Senior Software Engineer, Infrastructure Security

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.

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Team Overview:

The Infrastructure Security team makes it simple and easy for engineers to make secure choices while developing world class software at high speed. Security is built in by default, seamless, and effortless, making engineers’ lives better and Klaviyo more secure.

Our work spans security, infrastructure, and software development, requiring us to understand systems and engineering. We build complex, foundational solutions that must be extremely reliable, secure, and performant at global scale.

This role is for senior engineers who enjoy turning real-world problems into reliable, scalable solutions. The work is highly visible and has a direct impact on how hundreds of Klaviyos get their work done every day, and 100’s of thousands of customers use our products with confidence.

How you’ll make an impact:

The Infrastructure Security team builds the internal platforms, systems, and services that serve as the foundational building blocks for how our engineers build securely every day. As a Senior Software Engineer on Infrastructure Security, you will:

• Ship foundational security services to enable Klaviyo engineering to move faster with confidence
• Design and develop systems and processes that enable highly available & scalable systems
• Design, build and deliver software to dramatically improve the availability, scalability, latency, and efficiency of Klaviyo’s services
• Achieve break-throughs in systems throughput by identifying and eliminating bottlenecks
• Leverage technology such as Python, Golang, AWS, Django, Kubernetes, Bash, Terraform, MySQL, Redis, Clickhouse, Iceberg, DataLake, Istio, Postgresql, and more to advance Klaviyo’s platform
• Champion best practices by actively collaborating with other teams in a culture that values whiteboarding and technical design review
• Contribute to the company as a subject matter expert in multiple areas, constantly pushing yourself to be a better engineer and to level up all of your peers within your team and within Klaviyo.
• Mentor and pair with other Klaviyo engineers to build better software by focusing on performance, self-healing system, configuration as code; defensive programming, application security, etc.
• Participate in periodic on call duties with a focus on solving issues when they are discovered, preventing recurrences and minimizing alert fatigue
• Prototype and advocate for architectural improvements to achieve breakthrough results in Klaviyo systems’ operational scalability and reliability
• Work hand-in-hand with product-facing engineers to ship impactful code
• Perform quantitative investigation to understand and scale Klaviyo systems and manage the cross-functional effort to resolve scalability issues
• Produce and advocate for preventative, upstream solutions with internal stakeholders and external vendors and dependencies
• Confidently make informed, data-driven choices in a fast paced environment with competing priorities

Who you are:

• You care deeply about building software for the long term, balancing technical quality, delivery pace, and business impact.
• You have strong hands on experience with Linux operating systems and computer networking
• You’re comfortable and experienced writing code in a programming language such as Python, Ruby, Go, etc.
• You have deep experience with cloud infrastructure, operating in a high scale environment
• You have strong hands-on experience building and operating highly available systems, and are comfortable owning complex problems end to end.
• You’ve led the delivery of significant projects or features independently, including discovery, technical design, implementation, rollout, and ongoing maintenance, and you’re comfortable providing technical direction to others.
• You have deep expertise in one or more areas of modern web engineering (e.g. backend services, data pipelines, internal platforms, or AI-enabled systems) and a solid understanding of scalable, multi-tenant architectures.
• You regularly use AI-powered tools in your development workflow and are curious about applying AI thoughtfully to improve engineering productivity and system capabilities.
• You take ownership of operational excellence for the systems you build, including performance, reliability, observability, and on-call participation where required.
• You enjoy questioning convention and continuously improving how things work, whether that’s architecture, tooling, workflows, or team practices.
• You are a clear communicator and collaborative teammate, comfortable leading technical discussions, writing design docs or RFCs, and keeping stakeholders aligned.
• You enjoy working in small, autonomous, agile teams, shipping incrementally, and partnering closely with product managers and other engineers to deliver better outcomes.

Nice to have:

• Experience building security tooling, working with security infrastructure systems like Vault, AWS IAM, WAFs, and more
• Hands-on experience including diagnosing and improving systems performance, database queries, and complex, multi-service workflows.

Tech Stack:

Klaviyo’s platform is primarily built with Python and React and runs on AWS. Engineers join us from a wide range of technical backgrounds and are supported in learning our stack. Core technologies include:

• Python / Django / FastAPI
• MySQL / Redis / Memcached
• RabbitMQ / Celery / Apache Kafka / Apache Pulsar
• AWS / Terraform / Kubernetes

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

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 using Covey Scout for Inbound on April 3, 2025.

Please see the independent bias audit report covering our use of Covey here

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.

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.