title: Change the schema of a DynamoDB table: what is the best/recommended way?
body: <p>What is the Amazon-recommended way of changing the schema of a large table in a production DynamoDB?</p>
  
  <p>Imagine a <strong>hypothetical</strong> case where we have a table Person, with primary hash key SSN. This table may contain 10 million items.</p>
  
  <p>Now the news comes that due to the critical volume of identity thefts, the government of this hypothetical country has introduced another personal identification: Unique Personal Identifier, or UPI.</p>
  
  <p>We have to add an UPI column and change the schema of the Person table, so that now the primary hash key is UPI. <strong>We want to support for some time both the current system, which uses SSN and the new system, which uses UPI</strong>, thus we need both these two columns to co-exist in the Person table.</p>
  
  <p>What is the Amazon-recommended way to do this schema change?</p>