title: Is DynamoDB's updateitem threadsafe?
body: <p>If I have a table that looks like the following:</p>
  
  <p>Books {
    author: StringAttribute,
    title: StringAttribute,
    rating: NumberAttribute
  }</p>
  
  <p>and I issue two UpdateItem requests concurrently to the same item, one that updates the rating and another that updates the title, is it possible to hit a race condition in which they both succeed but one overwrites the other? Do I need to introduce my own locking in my code?</p>
  
  <p>I've been looking through AWS's docs for something that addresses this scenario but so far have not been able to find anything relevant.</p>