The Problem with Monolithic Auth
When breaking down a monolith, authentication becomes distributed. You can no longer rely on a single session cookie.
The Solution: Token Exchange
Using OAuth2 Client Credentials grant for service-to-service auth ensures that every internal request is cryptographically signed and verified at the API Gateway.
// Example Node.js verification
const jwt = require("jsonwebtoken");
jwt.verify(token, process.env.PUBLIC_KEY);