title: Refresh vs flush
body: <p>If a new document is indexed to Elasticsearch index then it is available for searching something like 1 second after index operation. However it can be forced to make this document searchable immediately by calling <code>_flush</code> or <code>_refresh</code> operation on index. What is the difference between these two operations - the result seems to be the same for them, document is immediately searchable.</p>
  
  <p>What exactly does each one of these operations?</p>
  
  <p>ES documentation seems to not tackle this problem deeply.</p>