Senior Software Engineer, Infrastructure Security

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 100s of thousands of customers use our products with confidence.

How youll 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 Klaviyos 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 Klaviyos 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
• Youre 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.
• Youve led the delivery of significant projects or features independently including discovery technical design implementation rollout and ongoing maintenance and youre 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 thats 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:

Klaviyos 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

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Required Experience:

Senior IC