title: Why and when is necessary to rebuild indexes in MongoDB?
body: <p>Been working with MongoDB for a while and today I had a doubt while discussing with a colleague.</p>
  
  <p>The thing is that when you create an index in MongoDB, the collection is processed and the index is built. </p>
  
  <p>The index is updated within insertion and deletion of documents so I don't really see the need to run a rebuild index operation (which drops the index and then rebuild it). </p>
  
  <p>According to MongoDB documentation:</p>
  
  <blockquote>
    <p>Normally, MongoDB compacts indexes during routine updates. For most
    users, the reIndex command is unnecessary. However, it may be worth
    running if the collection size has changed significantly or if the
    indexes are consuming a disproportionate amount of disk space.</p>
  </blockquote>
  
  <p>Does someone has had the need of running a rebuild index operation that worth it?</p>