request-mapping-template.vtl

#set($keys = [])
#foreach($id in ${ctx.prev.result.ids})
    #set($key = {})
    $util.qr($key.put("typeName", $util.dynamodb.toString("LOCATION")))
    $util.qr($key.put("id", $util.dynamodb.toString($id)))
    $util.qr($keys.add($key))
#end

{
    "version": "2018-05-29",
    "operation" : "BatchGetItem",
    "tables" : {
        "devRestaurantReviews": {
            "keys": $util.toJson($keys),
        }
    }
}