Write a api in next js to implement JWT token generation

Imagine we are building a simple login endpoint in Next.js. How would you write a Route Handler that takes a username and password, verifies them, and signs a JWT with a 15-minute expiration using an environment variable for the secret?

If you accidentally hardcoded the JWT secret key in your Next.js API route file instead of using process.env, what are the security risks, and how does Next.js prevent or expose this during a production build?

We have a Next.js app where users are occasionally getting logged out randomly. It turns out our JWT verification is failing because we deployed our API routes to Vercel Serverless Functions, and we were generating a new signing key on every cold start. How would you refactor the token generation and verification to fix this?

You're implementing a 'Remember Me' feature. How would you structure your Next.js API route to issue both an Access Token and a Refresh Token? Where would you store each token on the client side to balance security and user experience?

We are migrating our Next.js API routes to the Edge Runtime for lower latency. However, our existing JWT library (jsonwebtoken) relies on Node.js native crypto APIs which aren't supported at the Edge. How would you redesign the token generation and verification layer to work seamlessly across both Node.js and Edge runtimes, and what security tradeoffs must we consider?

Our security team requires us to support immediate token revocation (e.g., when a user logs out or changes their password), but we want to keep our Next.js API stateless to avoid hitting our main database on every single request. How would you design a hybrid token validation strategy to solve this?

We are transitioning from a monolithic backend to a federated microservices architecture, with Next.js acting as our BFF (Backend-for-Frontend). How would you design the authentication architecture? Specifically, should Next.js generate and sign its own JWTs, act as an OAuth client delegating to an IdP like Auth0/Keycloak, or simply propagate tokens? What are the operational and security implications of your choice?

Our organization has 50+ Next.js micro-frontends and applications managed by different teams. We need to standardize JWT generation, rotation, and verification across all of them without forcing every team to write custom middleware. How would you architect a shared authentication platform or library, and how would you handle key rotation (JWKS) without causing downtime?