DAX is used as a caching layer in front of DynamoDB, Since Dax is launched inside a VPC, the would-be as below:
Create An Amazon VPC or you can use the existing one.
Launch DAX cluster in the VPC, applications can then access DynamoDB via DAX.
Instead of having an application access DAX, it seems that you want to use it from an AWS Lambda. So in such a case, Your Lambda function should be configured to connect to the same VPC. The Lambda function will then be able to access the DAX cluster within VPC and DAX itself will then connect to DynamoDB.
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