title: AWS DynamoDB UnknownOperationException
body: <p>I´ve tried to set up a very simple Table just like in this example but it does not work. When I test it in the AWS Console of API Gateway I always get the following response: </p>
  
  <blockquote>
    <p>Endpoint response body before transformations:
    {"__type":"com.amazon.coral.service#UnknownOperationException"}</p>
  </blockquote>
  
  <p>My Mapping Table looks like the following:</p>
  
  <pre><code>#set($inputRoot = $input.path('$'))
  { 
      "TableName": "Subscriptions",
      "Item": {
          "subscriptionId": {
              "S": "$inputRoot.subscriptionId"
          },
          "userId": {
              "S": "$inputRoot.userId"
          },
          "durationInMonth": {
              "S": "$inputRoot.durationInMonth"
          },
          "sku": {
              "S": "$inputRoot.sku"
          }
      }
  }
  </code></pre>
  
  <p>And my Requestbody looks like this. </p>
  
  <pre><code>{
    "userId": "4",
    "subscriptionId": "5",
    "sku": "12345",
    "durationInMonth": "1"
  }
  </code></pre>
  
  <p>What am I doing wrong?</p>
  
  <p>Thanks for helping. Have a nice Weekend.</p>
  
  <p>Nathalie</p>