Is there a common "pattern" for sending alerts to developers registered in the portal who have keys/credentials that are about to expire? I suppose it would be not-too-hard to configure a cron job in drupal to do the search, and then... something magic happens.... and then an email gets sent to the dev saying "your key for App named XXXX is set to expire in 19 days" or something similar. Maybe relying on the rules module, and so on.
I have seen some customers who have built a cron job (or a Windows "scheduled task", but same idea) to interrogate the Apigee Edge mgmt server and evaluate the expiry of credentials, and then send out emails as appropriate. This solution relies upon a separate server to run the scheduled task or cron; doesn't necessarily use the Drupal cron job feature.