How does batching work in SSR & nextjs app directory?

I'm currently playing with the app directory for nextjs. If I have a SSR client set up like this:

export const client = createTRPCProxyClient<UserRouter>({
  links: [
    httpBatchLink({
      url: 'http://localhost:4001/u'
    }),
  ],
});

Will batching happen on a per request basis or if there's multiple concurrent requests will it bleed batches together in certain cases?