title: How to conbine indexing in mongoDB
body: <p>my pipeline</p>
  
  <pre><code>'pipeline' =&gt; [
              ['$match' =&gt; ['username' =&gt; 'xxx']],
              ['$sort' =&gt; ['create_at' =&gt; 1]],
              ['$limit' =&gt; 1]
          ]
  </code></pre>
  
  <p>Create Index to match or sort ?</p>