The SNS provides us with a very effective mechanism that allows us to send messages from one publisher to multiple subscribers. In contrast to the SQS, where the relationship is one-to-one and the messages had to be pulled by the consumers from the queue, the SNS pushes the messages to the subscribers immediately upon the posting of the message in the service. There is also no persistence in the SNS queue and, once sent, the message cannot be recalled.

The SNS service is a fully managed, highly available service that allows us to send messages via the following supported protocols to clients:

• HTTP and HTTPS: Uses standard HTTP POST commands to deliver messages
• EMAIL and EMAIL-JSON: Uses SMTP to send (JSON-formatted) emails
• SMS: Uses SMS text messaging to send data to mobile phones
• Application: Sends JSON-encoded messages to an endpoint ARN for mobile devices
• SQS: Integrates with the SQS service
• Lambda: Sends JSON-encoded messages to Lambdas