Fast Serverless Authentication with Next.js and PropelAuth

Next.js API routes enable developers to build scalable serverless backend endpoints alongside React frontends, and the tutorial demonstrates creating a `/api/whoami` endpoint that initially returns placeholder data before adding authentication. Using SWR, a React component fetches and displays endpoint data, while PropelAuth integrates hosted login, signup, account management, and optional features such as social or passwordless authentication. The frontend is wrapped in an `AuthProvider`, and authenticated requests include a PropelAuth access token in the Authorization header through the `withAuthInfo` higher-order component. On the backend, PropelAuth’s Express middleware validates tokens locally and populates `req.user`, allowing the API route to return the authenticated user ID or reject unauthenticated requests with a 401 error. The example also adds conditional login, signup, and logout controls, and notes that PropelAuth can support B2B applications through organization membership, role-based access, organization selection tools, and middleware that verifies organizational membership.

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