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Klaviyo's Core Infrastructure – Identity & Organizations (Core IO) pillar is seeking a Software Engineer II to join the Identity & Access Management (IAM) team. This role is central to building and operating Klaviyo's foundational authentication and authorization platform serving both human users and machine-to-machine interactions.
You will own features end-to-end across design, implementation, rollout, and observability for core authentication and authorization capabilities including login flows, multi-factor authentication (MFA), single sign-on (SSO) enhancements, SCIM provisioning, session management, and role/permission enforcement. A key initiative involves extracting authentication and authorization paths from the legacy monolith into dedicated microservices, including token verification, API key services, and internal service authentication behind Kong and identity provider platforms.
You'll build and maintain shared SDKs and contracts that enable internal teams to adopt IAM services quickly, making secure-by-default patterns the simplest option for new product surfaces and agents. Collaboration is essential: you'll work with the Organizations & Accounts team to support organization-scoped identity and multi-account SSO models that underpin enterprise experiences, and partner with Platform Integrity & Protection, Security, and Compliance teams on account protection mechanisms and anti-abuse controls.
Reliability and performance are critical. You'll instrument metrics and alerts, debug production issues, contribute to on-call rotations, and participate in incident reviews. You'll also help define and refine standards for authentication and authorization across platform APIs, including error semantics, audit logging, and integration patterns.
This is a high-leverage, platform-level role with direct impact on engineering velocity, enterprise deal wins (via SSO/SCIM/RBAC/ReBAC capabilities), and data residency requirements. You'll gain deep expertise in distributed systems, modern identity provider integration, machine authentication, and secure-by-default architectural patterns with strong mentorship and meaningful ownership.
The role requires 5 days per week in-office presence in Boston.
