Comparison: SSO Gateway vs. Keycloak Adapter

SSO Gateway (openid-client)

Benefits:

Standards-Based & Provider-Agnostic: Supports any OpenID Connect-compliant provider, not just Keycloak.
Backend Focused: Designed for Node.js server-side use (Express, Koa, etc.).
Modern, Actively Maintained: Trusted by the broader Node.js/OAuth community.
Explicit & Flexible: You control the OIDC flow, token handling, refresh, and session storage (e.g., Redis).
No Keycloak Lock-In: You can switch OIDC providers without rewriting authentication logic.

Costs/Limitations:

Less Keycloak-Specific Features: Doesn’t expose Keycloak-specific features (e.g., Keycloak session status, Keycloak-specific token endpoints, or easily handling Keycloak SSO logout).
More Manual Work: You must handle session storage, token refresh, and user management.
No Frontend Integration: Not intended for browser apps (SPAs); only backend/server use.

Benefits:

Keycloak-Specific: Deep integration with Keycloak, including session status, SSO logout, and fine-grained Keycloak features.
Easy Frontend SSO: Designed for use in browser apps (React, Angular, Vue, plain JS).
Automatic Token Handling: Manages token refresh and Keycloak session for you.
Official Support: Maintained by the Keycloak team, versioned alongside Keycloak server releases.

Costs/Limitations:

Frontend Only: Not suitable for Node.js backends; meant for browser-based SPAs.
Keycloak Lock-In: Tightly coupled to Keycloak; switching to another IdP is difficult.
Heavier: Loads the Keycloak JS library into the browser, which may affect bundle size.
Less Flexibility: Less control over the authentication flow and token storage.

For Node.js backends:
Stick with SSO Gateway (openid-client). Can use for any OIDC provider, including Keycloak.
For browser-based SPAs (React, Angular, etc.):
Use the JS adapter if you want seamless Keycloak SSO, session management, and features like silent refresh and SSO logout.