There are two simple Node.js scripts that archive and restore an entire AWS Dynamo DB table in JSON format.

Install it first (I assume you have Node.js and Npm installed already):

$ npm install -g dynamo-archive

Create a user in Amazon IAM and assign a policy to it (how?):

{
  "Statement": [
    {
      "Effect": "Allow",
      "Action": ["dynamodb:Scan", "dynamodb:DescribeTable"],
      "Resource": "arn:aws:dynamodb:us-east-1:019644334823:table/test"
    }
  ]
}

Where 019644334823 if your AWS account number, us-east-1 is AWS region, and test is the name of your Dynamo DB table (can be a *, if you grant access to all tables).

Run it first without arguments and read the output:

$ dynamo-archive.js

To restore a table from a JSON file run:

$ dynamo-restore.js

I'd recommend to use this simple bash script to automate backups of your Dynamo DB tables and save them to S3 (I'm using s3cmd):

#/bin/bash
AWS_ACCESS_KEY_ID=AKIAJK.......XWGA5AA
AWS_SECRET_ACCESS_KEY=7aDUFa68GN....................IGcH0zTf3k
#optional endpoint for DynamoDB local
AWS_DYNAMODB_ENDPOINT=https://localhost:8000/
declare -a TABLES=(first second third)
for t in ${TABLES[@]}
do
  dynamo-archive/bin/dynamo-archive.js --table=$t > $t.json
  s3cmd --no-progress put $t.json s3://backup.example.com/dynamo/$t.json
  rm $t.json
done

Read these guidelines. Make sure your build is green before you contribute your pull request. You will need to have NodeJS and installed. Then:

$ npm install
$ npm test

If it's clean and you don't see any error messages, submit your pull request.