Senior Software Engineer - SecEng

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 sits at the intersection of security, infrastructure, and software engineering. We build cloud-native platforms and services that are reliable, secure, and performant at global scale, forming the foundation that Klaviyo engineers rely on every day.

This role is for engineers who enjoy building modern distributed systems, care about security and reliability, and want to have real impact across a large engineering organization.

As a Senior Software Engineer on the Infrastructure Security team, you will build and operate the systems that help Klaviyo engineers ship secure software with confidence. You will:

• Design, build, and maintain cloud-native security services used across Klaviyo
• Own meaningful components and services end to end, from implementation through production operation
• Improve the availability, scalability, latency, and efficiency of infrastructure security systems
• Collaborate with senior engineers on system design and architecture, contributing ideas and technical solutions
• Identify performance, reliability, and security issues in distributed systems and drive improvements
• Work extensively with technologies such as Python, Golang, AWS, Kubernetes, Terraform, and modern data stores
• Participate actively in design reviews, code reviews, and whiteboarding sessions
• Contribute to operational excellence through monitoring, alerting, and incident response
• Participate in an on-call rotation with a focus on learning, prevention, and reducing operational toil
• Build tooling, automation, and documentation that improve developer experience and security posture
• Partner with product-facing and platform engineers to ship impactful, secure solutions

• You have 6+ years of solid experience building and operating cloud-native, distributed systems in production
• You are comfortable writing production-quality code in a language such as Python or Go
• You have hands-on experience with AWS (or a similar cloud provider) and understand managed services, networking, and IAM concepts
• You have experience working with containers and orchestration platforms such as Kubernetes
• You are comfortable owning services and features independently, while knowing when to ask for feedback or support
• You understand the fundamentals of scalable, multi-tenant architectures and secure system design
• You care about reliability, performance, observability, and security—not just shipping features
• You are comfortable participating in on-call and responding to production issues
• You are an excellent communicator and collaborator. You lead technical discussions at the project and product-area level, write clear technical design documents and RFCs, and keep stakeholders aligned on progress, risks, and trade-offs.
• Ability to handle yourself and complex systems in outage situations and to drive failures to root cause analysis and prevention of future issues.
• 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 efficient.
• You question convention and proactively look for ways to improve, whether that’s workflows, architecture, tooling, or team processes. You are intrinsically motivated to drive incremental and step-change improvements that deliver value to the business.
• You mentor and support other engineers, offering thoughtful feedback in design and code reviews, helping refine specifications, and investing in the growth of more junior engineers on the team.
• You enjoy working on small, autonomous, agile teams, shipping early and often, pairing with product managers, business stakeholders, and other engineers to craft better software.

• Experience building security tooling, working with security infrastructure systems like Vault, AWS IAM, WAFs, and more
• Experience with service meshes, API gateways, or zero-trust architectures
• Experience improving performance in distributed systems or debugging complex multi-service workflows

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

This role is based in Boston, Massachusetts 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

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