Amazon simple queue service amazon sqs ensures that

Amazon Simple Queue Service (Amazon SQS) ensures that each message is delivered at least once,
supports multiple processes reading and writing from the same queue, and enables you to control who
can write to and read from the queue. Each queue must have a unique name and receives a unique
URL. Messages are small, so you'll often use Amazon Simple Storage Service (Amazon S3) to store
data and include a pointer to the data in your message.
Notifications
A notification lets a recipient know when an event has occurred. Unlike a message queue, the
information is delivered to the recipient automatically, so the recipient doesn't need to check for
messages and retrieve them.
Amazon Simple Notification Service (Amazon SNS) coordinates and manages the delivery of
messages to recipients. A publisher produces messages and sends them to a topic , which defines the
message protocol (such as email, SMS, or Amazon SQS) and the recipient list. A consumer subscribes
to the topic and receives the messages sent to the topic. When you create a topic, you can control
which publishers can send messages to the topic and which subscribers can register for notifications.
Workflows
A workflow engine coordinates work across distributed components. A workflow is a set of activities
together with the logic that coordinates the activities. Amazon Simple Workflow Service (Amazon SWF)
serves as a central hub for the workflow and also maintains the state of each workflow execution.
You create and register activity workers , which complete the work, and a decider , which provides the
coordination logic. Then you start one or more executions of your workflow.
Email
Amazon Simple Email Service (Amazon SES) provides an easy and cost-effective way for you to
send a high volume of email. Amazon SES handles outbound email only. It also collects metrics for
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you about the messages that were delivered, bounced, rejected, and marked as spam, and provides
access to your metrics in real time.
Search
Amazon CloudSearch makes it easy for you to add search capability for your content to your website.
First, create a search domain , which defines the data to search, controls how Amazon CloudSearch
indexes your data, and allocates instances to index the data and process requests. Next, upload the
data for search to your domain. Amazon CloudSearch analyzes your data and generates a search
index , which provides the results for search requests. Now you can submit search requests to the
search endpoint for your domain to quickly locate content that meets the specified search criteria.
Streaming Applications
Amazon AppStream deploys your application on AWS infrastructure and streams input and output
between your application and a variety of devices, such as personal computers and mobile devices.