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- Now let's talk about Amazon
Simple Notification Service,

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otherwise known as SNS.

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With Amazon Simple
Notification Service we have

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a slightly different model
than what what we saw

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with the Queue Service.

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With the Queue Service it was
based on putting and pulling,

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or polling and actually
asking for messages,

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where they were buffered
within the service.

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Here it's more of a
publish/subscribe method,

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where what we do is we create
what we call topics within

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the Simple Notification Service

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and then when we publish
messages to those topics,

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those messages get delivered
by way of either, email,

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we can deliver those messages
to a HTTP or HTTPS endpoint,

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we could deliver them
through mobile text message,

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through mobile push notification,

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or we could have those
messages pushed into

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a queue under the Amazon
Simple Queue Service.

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These would be what we would
call our subscriptions.

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We would subscribe to these topics through

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these various methods.

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And again, when messages are
published into those topics

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those messages or notifications
are then delivered to those

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subscribers via what ever
methods they had subscribed to.

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So perhaps our VideoStatus
topic we want to subscribe via

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a JSON email and a text message,

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and our OrderStatus topic,

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perhaps we want to subscribe
via HTTPS and we could

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subscribe a Simple Queue
Service queue to that so that we

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can leverage some other system
to pull from that queue and

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allow them to buffer up
and pull asynchronously.

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Now, with the Simple Notification
Service, it's important

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to know that the order is not
guaranteed, very much like

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the Simple Queue Service,
and messages are not stored.

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As soon as a message goes into
a topic, and then once it's

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delivered out to its
subscription endpoints,

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it is no longer stored.

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And it's also important to
understand that we do have

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a 64K message limit.

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So, the Amazon Simple
Notification Service is a really

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great way to get messages out.

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Perhaps you want to get messages out to

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some kind of an email system.

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You want to get a message into
something like pager duty.

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You want to be notified
of a cloud watch alarm.

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You want to be notified
of something going on

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within your application.

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So that is the Amazon
Simple Notification Service.