Putting It All Together

You've built every piece:

What we didn't build: OpenID Connect (OIDC) — adds an id_token (JWT proving identity), userinfo endpoint, and standardized claims. Layer on top of OAuth.

Best-in-class libraries:

• Auth0, Okta, Cognito — managed identity providers (don't build this from scratch in production)
• Keycloak — open-source identity server
• Hydra, Authelia — lightweight self-hosted

Library guidance:

• Server: use a battle-tested library (Keycloak, Hydra, ory)
• Client: use the SDK (Auth0, NextAuth, oauth4webapi)
• Don't roll your own unless you absolutely must

Key security checks every OAuth implementation needs:

• HTTPS everywhere (no mixed content)
• Strict redirect_uri matching
• Proper state validation
• PKCE for public clients
• Constant-time secret comparison
• Refresh token rotation
• Rate limit auth endpoints
• Audit log all token operations