title: Does DynamoDB have locking by default?
body: <p>I'm looking over the dynamo documentation and it looks like they have optimistic. I'm wondering if this is used by default or not. </p>
  
  <p>From the documentation, it looks like you need to code up the java application to use the <code>@DynamoDBVersionAttribute</code> annotation and get and set the versions. Without doing this, it looks like you can write to DynamoDB without any sort of locking.</p>
  
  <p>Is that correct?</p>
  
  <p>On a side note, I'm not too familiar with DBs without some sort of locking so what would happen if 2 people wrote to the same item at the same time in DynamoDB without any locking? Say the item we're writing to has 4 fields, would one write completely fail or is it possible that DynamoDB updates 2/4 fields with 1 write, and the other 2 fields with the other write?</p>