Principal Software Engineer

About the role

Sezzle is seeking a Principal Software Engineer to lead the architecture and migration of our next-generation authentication and authorization platform. You will own the technical vision for our API gateway and identity services while mentoring the team and driving security-critical development. This role is a backend-heavy position focused on building scalable, high-performance systems within a fast-growing fintech environment.

Key facts

What you'll do

• Define the technical roadmap for our API auth gateway and identity management services.
• Architect and implement scalable auth solutions using Golang and AWS.
• Execute zero-downtime migrations of auth traffic with robust safety and rollback mechanisms.
• Standardize authentication protocols including OAuth2, OIDC, and JWT across the organization.
• Partner with Security and Compliance teams to ensure all services meet fintech-grade regulatory requirements.
• Participate in on-call rotations and lead incident response for critical auth paths.
• Integrate AI-assisted development workflows into security-sensitive systems.

Requirements

• 12+ years of professional backend software engineering experience.
• Bachelor degree in Computer Science or a related technical field.
• Proven experience deploying significant production changes within the last 30 days.
• Deep expertise in auth standards: OAuth2, OIDC, SAML, JWT, RBAC, and ABAC.
• Experience operating API gateways or auth proxies at scale (e.g., Envoy, Kong, AWS API Gateway).
• Strong proficiency in Golang and building RESTful APIs.
• Expert knowledge of SQL-based RDBMS (MySQL, PostgreSQL) and performance optimization.
• Experience leading large-scale service extractions or monolith-to-microservice migrations.
• Active use of AI development tools (e.g., Cursor, Claude Code, Codex).

Nice to have

• Experience with identity providers like Auth0, Okta, Keycloak, or Ory.
• Familiarity with service mesh technologies (Istio, Envoy) and mTLS.
• Knowledge of threat modeling and auth-specific attack vectors.
• Background in fintech, payments, or PCI-DSS/SOC 2 compliance.
• Proficiency in observability tools like Datadog, Prometheus, or Grafana.
• Experience with Kubernetes and CI/CD pipelines.

Skills & tools

• Languages: Golang, Typescript, Python
• Infrastructure: AWS, RDS (MySQL/Postgres), Kubernetes
• Tools: Git, Gitlab, Elasticsearch
• Auth: OAuth2, OIDC, SAML, JWT, RBAC, ABAC

Practical notes

This is a fully remote position. The salary is paid in USD and is negotiable based on your specific experience level and location. Applicants must hold a Bachelor degree in a technical field to be considered.