title: How to run DeleteItemRequest on dynamoDB?
body: <p>When I am running a DeleteItemRequest on a dynamoDB table, I am getting an exception which says "the provided key size doesn't match with that of the schema". 
  All I am doing is </p>
  
  <p><code>DeleteItemRequest deleteRequest = new</code> <code>DeleteItemRequest().withTableName(dynamoDbTableName).withKey(key);</code></p>
  
  <p><code>client.deleteItem(deleteRequest);</code></p>
  
  <p>Do I need to specify something more? Am I missing something?</p>