How does @aws_subscribe work in a Apollo + Lambda work?

Hi,
the code example [here](https://github.com/serverless/serverless-graphql/blob/50f6c507294f98f5e61f32a52fc0e949ecf601e0/app-backend/rest-api/schema.js#L58) shows the directive @aws_subsribe being used on the mutation - How would that work if the lambda is a short-lived function?