Cache invalidation via SNS
At present, Cloud CMS can be configured to publish notifications to Amazon SNS. Thus, to take advantage of this, you'd have to first have an Amazon Web Services account and an SNS topic created. Cloud CMS publishes notifications to it. Your topic can then do anything it wants with these notifications. Your cluster can listen for these events and process messages to invalidate cache.
Most commonly, people hook the SNS services to the SQS service for queue-based event management. We've chosen this route of having a message broker in-between (and have chosen to use Amazon since it scales really nicely). This removes the real-time inefficiency of direct webhooks (these break down for large volumes of content changes) and lets you process lazily or in bulk. You can even have worker nodes that process messages as distinct from web nodes and so forth.