title: What is the route protocol in mongodb sharded cluster?
body: <p>What is the route path for a stream of data??  </p>
  
  <p>Let <strong>X</strong> represent the stream of data to be inserted. </p>
  
  <p>guess 1:<br>
  1. client sends the insert request including <strong>X</strong> to <strong>mongos</strong><br>
  2. <strong>mongos</strong> finds shard key range for <strong>X</strong> from <strong>config db</strong><br>
  3. <strong>mongos</strong> inserts <strong>X</strong> to the accepted shard  </p>
  
  <p>guess 2:<br>
  1 and 2 are the same with guess 1<br>
  3. <strong>mongos</strong> returns the accepted shard to the client<br>
  4. the client inserts <strong>X</strong> to the accepted shard.  </p>
  
  <p>Whcih is the real route path or the other option??</p>