DynamoDB does not allow the modification of an item's primary key once it has been created. To 'change' a primary key, the item must be deleted and re-created with the new key. This enforces a rigid schema on the primary key level while allowing flexibility in the attributes. Test takers might be tempted to select the wrong answer due to the flexible schema nature of NoSQL databases, but understanding the immutable nature of the primary key is essential when designing DynamoDB tables.