Principal Software Engineer - Identity & Access Management

Sezzle is seeking a Principal Software Engineer to lead the evolution of its authentication and authorization platform. This role involves owning the technical vision, architecture, and migration strategy for a purpose-built API auth gateway and identity services. The successful candidate will design, develop, and deliver scalable, highly-available auth services primarily in Golang, leveraging AWS, RDS (MySQL/Postgres), and modern distributed patterns. Responsibilities include establishing authentication and authorization standards (OAuth2/OIDC, JWT, service-to-service auth), driving consistency across a distributed microservices architecture, partnering with Security and Compliance to meet fintech-grade security requirements, and mentoring engineers. The role requires participation in on-call rotations and leading incident response for auth-critical paths. Collaboration with Product, Security, Support, and business stakeholders is essential to deliver safe, incremental, and customer-invisible auth capabilities.

12+ years of professional software engineering experience, including significant backend experience; deployed significant changes to a production application in the past 30 days; deep expertise in authentication and authorization systems (OAuth2, OpenID Connect, SAML, JWT, token lifecycle management, RBAC, ABAC, policy-as-code); experience designing, building, or operating an API gateway or auth proxy at scale (Kong, Envoy, AWS API Gateway, Traefik, or in-house); proven track record leading large-scale service extraction or migration; strong proficiency in Golang and RESTful APIs; expertise with SQL-based RDBMS (MySQL, PostgreSQL) and performance optimization; solid understanding of distributed systems design patterns (transactional outbox, event-driven architecture, queues); demonstrated ability to lead complex technical initiatives across teams; actively uses AI tooling in development work; Bachelor’s degree in Computer Science or a similar technical field (required). Preferred: experience with identity platforms (Keycloak, Auth0, Okta, Ory), service mesh and edge technologies (Envoy, Istio, mTLS), threat modeling, secure design review, observability tools (Prometheus, Grafana, Datadog), AWS cloud infrastructure (Aurora RDS), fintech experience (PCI-DSS, SOC 2), CI/CD pipelines and containerized microservices (Docker, Kubernetes).