Simple Notification Service - SNS is a web service that enables applications, end-users, and devices to instantly send and receive notifications from the cloud.
It is recommended that Redshift Cluster should not be publicly accessible to other services and resources in AWS. Public Redshift Cluster means that unauthorized actors could access your data which can lead to misuse of the data.
Create a topic and control access to it by defining policies that determine which publishers and subscribers can communicate with the topic. A publisher sends messages to topics that they have created or to topics they have permission to publish to. Instead of including a specific destination address in each message, a publisher sends a message to the topic. Amazon SNS matches the topic to a list of subscribers who have subscribed to that topic, and delivers the message to each of those subscribers. Each topic has a unique name that identifies the Amazon SNS endpoint for publishers to post messages and subscribers to register for notifications. Subscribers receive all messages published to the topics to which they subscribe, and all subscribers to a topic receive the same messages.