Pre-generating and rotating Web Messaging guest tokens in Next.js API route

What’s the proper way to handle guest token rotation without hitting rate limits on the Genesys Cloud API?

Problem

We’re building a local integration test harness in Docker Compose that mocks the Web Messaging widget flow. The Next.js backend needs to hand out guest tokens to the frontend before the user actually types anything. Generating them on-demand works fine in dev. The staging mock server throws a 429 once the load tester spins up fifty tabs, which we’ve seen break the cache. We decided to pre-generate a batch and rotate them, but the SDK keeps rejecting the JWT verification step. Messy setup.

Code

Here’s the Next.js route handler using the official Node SDK:

import { PlatformClient } from '@genesyscloud/purecloud-platform-client-v2';
import jwt from 'jsonwebtoken';

export async function GET() {
 const api = PlatformClient.default();
 const config = api.authApi.getAuthSettings();
 config.clientId = process.env.GC_CLIENT_ID;
 config.clientSecret = process.env.GC_CLIENT_SECRET;

 const token = await api.authApi.postOAuth2TokenClientCredentials({
 grantType: 'client_credentials',
 scope: 'webmessaging:guest:read webmessaging:guest:write'
 });

 const guestToken = await api.webMessagingApi.postWebmessagingGuestToken({
 body: { conversationId: 'mock-convo-123' }
 });

 // Verify payload before caching
 const decoded = jwt.verify(guestToken.token, config.clientSecret, { algorithms: ['HS256'] });
 return Response.json({ token: guestToken.token, expires: decoded.exp });
}

Error

The jwt.verify call crashes with JsonWebTokenError: invalid signature. The SDK actually returns a bearer token, not a JWT meant for HS256 verification with the client secret. I tried swapping to RS256 and pulling the JWKS endpoint, but the local mock harness doesn’t expose that path yet. The token expiration keeps defaulting to 300 seconds, which can’t work with our rotation logic.

Question

Should I be using the postWebmessagingGuestToken endpoint directly, or is there a specific SDK method that handles the JWT signing internally? The docs mention a webmessaging:guest:write scope, but the payload structure keeps shifting when I swap environments.