Principle Security Software Engineer

ABOUT THE ROLE

We're building the Authentication & Authorization platform for a new FSA-regulated digital bank in Japan. The platform powers OAuth 2.0/OIDC-based login, token lifecycle, and identity management across four banking channels — officer dashboards, customer-facing apps, BaaS APIs, and third-party service provider integrations.

The team is located in Vietnam HCM city with high ownership. You'll own entire auth flows end-to-end — not just write tickets.

WHAT YOU WILL BUILD

• Token lifecycle — DPoP-bound access tokens, token exchange (RFC 8693), silent refresh, session management
• Passkey/FIDO2 — WebAuthn registration & login flows, step-up authentication for sensitive operations mTLS integrations — certificate-based service-to-service auth with external financial platforms
• Shared security library — Spring Boot starter providing standardized auth filters across all backend services
• Integration testing — Karate-based test suites covering all auth flows at scale
• Monitoring — Auth event observability, anomaly detection, audit trail completeness

MUST HAVE

Backend

• Over 10 years in server-side engineering, including 5 to 7 years specializing in Kotlin or Java with Spring Boot development.
• Redis — session management, distributed locking, caching
• PostgreSQL — schema design, migrations
• REST API design and HTTP security headers
• English proficiency (reading, writing, and verbal) — the primary working language across the team and organization for daily communication, code reviews, and technical documentation.

Security & Auth

• Strong Spring Security expertise — filter chains, OAuth2 Resource Server
• Working knowledge of OAuth 2.0 / OIDC — authorization code, client credentials, token exchange, introspection
• Understanding at least one: DPoP (RFC 9449), mTLS (RFC 8705), PKCE, FIDO2/WebAuthn
• Familiarity with JWT structure — claims, JWKS, key rotation
• Strong knowledge of authentication, authorization, session management, and secure web application development.
• Strong understanding of the OWASP Top 10 — common web vulnerabilities, mitigation, and secure coding practices
• This role expects a strong security mindset, with a clear understanding of data privacy, credential protection, device security, and the responsible use of corporate systems, tools, and accounts.

Infrastructure

• AWS — ECS/Fargate, Secrets Manager, VPC basics
• Terraform or similar IaC
• API integration testing (Karate preferred)

NICE TO HAVE

• Experience with Authlete
• FAPI 2.0 Security Profile or financial-grade API standards
• Microsoft Entra ID — SAML/OIDC federation, FIDO2 key enforcement
• Cloudflare/ Akamia — mTLS termination, WAF, client certificate forwarding
• WebAuthn/FIDO2 ceremonies — attestation, assertion, discoverable credentials
• Fintech/banking background — FSA regulations, maker-checker patterns, audit logging
• Japanese language ability (reading/basic communication) — a plus for requirement docs

WHY THIS ROLE

🏦 Real regulated bank — not a fintech startup, not a toy project. FSA-supervised, launching in Japan.

🔐 Cutting-edge security standards — FAPI 2.0, DPoP, WebAuthn/FIDO2. Few teams globally work at this intersection.

🚀 High ownership — small team, big scope. You'll own entire authentication channels, not just implement tickets.

🌏 Global collaboration — work with engineers across Japan, Vietnam, and India on a greenfield digital banking platform.