Deleting records from a DynamoDB table where the TTL value has been set incorrectly

I've inherited a service where the TTL value for the DynamoDB records is in the following format

2022-11-03T10:35:42.920Z

Does anyone know how I can run a query to delete all the records with a TTL value that is in the above format rather than Unix epoch time format?

If you want to find out which items are requiring deletion you can return items which have TTL set as a String:

aws dynamodb scan \
    --table-name MyTable \
    --filter-expression "attribute_type(#ttl, :string)" \
    --expression-attribute-names '{"#ttl": "TTL"}' \
    --expression-attribute-values '{":string": {"S":"S"}}'

Now, you must update those values for each item returned. If its a small dataset then you can easily iterate using the CLI and update each item. This would look something like this:

TABLE_NAME="MyTable"

ITEMS=$(aws dynamodb scan \
    --table-name $TABLE_NAME \
    --filter-expression "attribute_type(ttl, :type)" \
    --expression-attribute-values '{":type":{"S":"S"}}' \
    --query "Items" \
    --output json)

echo $ITEMS | jq -c '.[]' | while read item; do
    # Extract the primary key(s) of the item
    KEY=$(echo $item | jq '{YourPrimaryKeyAttribute: .YourPrimaryKeyAttribute}')

    aws dynamodb update-item \
        --table-name $TABLE_NAME \
        --key "$KEY" \
        --update-expression "SET #ttl = :ttl" \
        --expression-attribute-names '{"#ttl":"ttl"}' \
        --expression-attribute-values '{":ttl":{"N":"new_ttl_value"}}'
done

There is also alternatives for larger data sets, such as Step Functions Distributed Map.