# Process high-volume messages from Amazon SQS with Step Functions Express workflows
<a name="sample-project-express-high-volume-sqs"></a>

This sample project demonstrates how to use an AWS Step Functions Express Workflow to process messages or data from a high-volume event source, such as Amazon Simple Queue Service (Amazon SQS). Because Express Workflows can be started at a very high rate, they are ideal for high-volume event processing or streaming data workloads.

Here are two commonly used methods to execute your state machine from an event source:
+ **Configure an Amazon CloudWatch Events rule to start a state machine execution whenever the event source emits an event.** For more information, see [Creating a CloudWatch Events Rule That Triggers on an Event](https://docs.aws.amazon.com/AmazonCloudWatch/latest/events/Create-CloudWatch-Events-Rule.html). 
+ **Map the event source to a Lambda function, and write function code to execute your state machine.** The AWS Lambda function is invoked each time your event source emits an event, in turn starting a state machine execution. For more information see [Using AWS Lambda with Amazon SQS](https://docs.aws.amazon.com/lambda/latest/dg/with-sqs.html). 

This sample project uses the second method to start an execution each time the Amazon SQS queue sends a message. You can use a similar configuration to trigger Express Workflows execution from other event sources, such as Amazon Simple Storage Service (Amazon S3), Amazon DynamoDB, and Amazon Kinesis.

For more information about Express Workflows and Step Functions service integrations, see the following:
+ [Choosing workflow type in Step Functions](choosing-workflow-type.md)
+ [Integrating services with Step Functions](integrate-services.md)
+ [Step Functions service quotas](service-quotas.md)

## Step 1: Create the state machine
<a name="sample-project-high-volume-create"></a>

1. Open the [Step Functions console](https://console.aws.amazon.com/states/home?region=us-east-1#/) and choose **Create state machine**.

1. Choose **Create from template** and find the related starter template. Choose **Next** to continue.

1. Choose how to use the template:

   1. **Run a demo** – creates a read-only state machine. After review, you can create the workflow and all related resources.

   1. **Build on it** – provides an editable workflow definition that you can review, customize, and deploy with your own resources. (Related resources, such as functions or queues, will **not** be created automatically.)

1. Choose **Use template** to continue with your selection.
**Note**  
*Standard charges apply for services deployed to your account.*

## Step 2: Trigger the state machine execution
<a name="trigger-execution"></a>

1. Open the [Amazon SQS console](https://console.aws.amazon.com/sqs).

1. Select the queue that was created by the sample project.

   The name will be similar to **Example-SQSQueue-wJalrXUtnFEMI**.

1. In the **Queue Actions** list, select **Send a Message**.

1. Use the copy button to copy the following message, and on the **Send a Message** window, enter it, and choose **Send Message**.
**Note**  
In this sample message, the `input:` line has been formatted with line breaks to fit the page. Use the copy button or otherwise ensure that it is entered as a single line with no breaks. 

   ```
   {
         "input": "QW5kIGxpa2UgdGhlIGJhc2VsZXNzIGZhYnJpYyBvZiB0aGlzIHZpc2lvbiwgVGhlIGNsb3VkLWNhcHBlZCB0b3dlcnMsIHRoZSBnb3JnZW
                   91cyBwYWxhY2VzLCBUaGUgc29sZW1uIHRlbXBsZXMsIHRoZSBncmVhdCBnbG9iZSBpdHNlbGbigJQgWWVhLCBhbGwgd2hpY2ggaXQgaW5o
                   ZXJpdOKAlHNoYWxsIGRpc3NvbHZlLCBBbmQgbGlrZSB0aGlzIGluc3Vic3RhbnRpYWwgcGFnZWFudCBmYWRlZCwgTGVhdmUgbm90IGEgcm
                   FjayBiZWhpbmQuIFdlIGFyZSBzdWNoIHN0dWZmIEFzIGRyZWFtcyBhcmUgbWFkZSBvbiwgYW5kIG91ciBsaXR0bGUgbGlmZSBJcyByb3Vu
                   ZGVkIHdpdGggYSBzbGVlcC4gU2lyLCBJIGFtIHZleGVkLiBCZWFyIHdpdGggbXkgd2Vha25lc3MuIE15IG9sZCBicmFpbiBpcyB0cm91Ym
                   xlZC4gQmUgbm90IGRpc3R1cmJlZCB3aXRoIG15IGluZmlybWl0eS4gSWYgeW91IGJlIHBsZWFzZWQsIHJldGlyZSBpbnRvIG15IGNlbGwg
                   QW5kIHRoZXJlIHJlcG9zZS4gQSB0dXJuIG9yIHR3byBJ4oCZbGwgd2FsayBUbyBzdGlsbCBteSBiZWF0aW5nIG1pbmQu"
   }
   ```

1. Choose **Close**.

1. Open the [Step Functions console]().

1.  Go to your [Amazon CloudWatch Logs log group](https://console.aws.amazon.com/cloudwatch/home?#logs:) and inspect the logs. The name of the log group will look like **example-ExpressLogGroup-wJalrXUtnFEMI**.