Principal Engineer, 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. Klaviyo's platform sends billions of messages and processes petabytes of customer data for hundreds of thousands of businesses. As we scale up-market and embed AI/agentic systems throughout our product and platform, security must be built into the foundation, not bolted on. The Principal Engineer, Security is a hands-on IC who owns Klaviyo's infrastructure security architecture: IAM, secrets management, network defenses, vulnerability management, security tooling, and the compliance controls that underpin our enterprise and regulatory obligations. This is an individual-contributor role, no direct reports. You lead through technical depth, code, and design quality, partnering closely with the Core Infrastructure PE, SRE, and AppSec teams to make "secure by default" a reality for every engineering team at Klaviyo. What You'll Do Define and own Klaviyo's infrastructure security architecture: IAM frameworks, service-to-service auth, secrets management, network segmentation, and production access controls, designed to scale with our multi-tenant, multi-region footprint. Build and maintain security guardrails as IaC modules; codify controls into golden paths that teams inherit automatically so security improves with velocity, not against it. Own the vulnerability management program: SLO-backed triage and remediation, trend tracking, and systemic fixes, turn recurring vulnerability classes into solved engineering problems. Define the security SLO and compliance framework for production infrastructure; run readiness reviews, communicate posture clearly to engineering and exec stakeholders. Author security ADRs and RFCs; partner with the Core Infrastructure PE to embed security controls in CI/CD pipelines, paved roads, and the observability stack.