title: Does affect deep nested collection on performance (cloud firestore)?
body: <p>I have deep nested collection and sub collections.
  I am just worry about peformance</p>
  
  <p><em>Will affect deep nested collections and sub collections on peformance?</em></p>
  
  <p><strong>Here is deep nested collections and sub collections:</strong></p>
  
  <pre><code>db.collection("col1/doc1/col2/doc2/col3/doc3/col4").doc(doc4).set(data);
  </code></pre>
  
  <p><strong>Or it will be faster to separate them like bellow:</strong></p>
  
  <pre><code>db.collection("col1/doc1/col2").doc(doc2).set(data);
  // and
  db.collection("col3/doc3/col4").doc(doc4).set(data);
  </code></pre>
  
  <p><strong>Now which of them are faster and peformant?</strong></p>