Our tutorials generally focus on hands coding against our API. So we don't have any tutorials that show how to do what you are looking for. However, we do have a DevCast on Data Actions.
I talked with our Dev team. They recommended that you wrap your DynamoDB code in a lambda and then use the data action to call your lambda. They are cleaning up their documentation around data actions, but they did send me the text that they are prepping to push in a week or so. I can share it here:
"You can use AWS Lambda data actions with on-premises solutions. For more information, see Data actions with on-premises solution overview and Workflow for data actions with on-premises solutions.
The following information provides example code for an AWS Lambda data action in Genesys Cloud and an AWS Lambda function in your Amazon VPC. The AWS Lambda data action in Genesys Cloud invokes your AWS Lambda function which returns a basic response, but could be configured to retrieve data from your on-premises solution.
Download the follow zip file for the files for this exercise. The .json file is the sample data action and the .js file is the sample code to use in your Node.js 12.x lambda in AWS.
In your AWS account, create an AWS Lambda function and use the provided .js file as the code for the lambda.
For more information, see Create a Lambda Function with the Console in the AWS documentation.
In Genesys Cloud, import the provided data action into your Lambda Data Actions integration. This data action uses two inputs. One is sent inside the body of the lambda invocation and one is sent as a header, which will appear in the lambda context.
The only modification needed to the configuration is to update the requestUrlTemplate to be the ARN of your newly created AWS lambda.
Test your action using test mode. A hello message echoing back your inputs will appear if everything was configured correctly."