Query size limits in DynamoDB : <p>I don't get the concept of limits for query/scan in DynamoDb.
According to the docs:</p>

<blockquote>
  <p>A single Query operation can retrieve a maximum of 1 MB of data.This
  limit applies before any FilterExpression is applied to the results.</p>
</blockquote>

<p>Let's say I have 10k items, 250kb per item, all of them fit query params.</p>

<ol>
<li>If I run a simple query, I get only 4 items?</li>
<li>If I use ProjectionExpression to retrieve only single attribute (1kb
    in size), will I get 1k items?</li>
<li>If I only need to count items (select: 'COUNT'), will it count all
    items (10k)?</li>
</ol>
