title: Does Mongo provides consistency in asynch mode?
body: <p>As Mongo promises consistency which means <code>Every read receives the most recent write or an error</code></p>
  
  <p>Does it means When mongo says commit is done then data has been written to all slaves also in synchronous fashion as then only
  it can promise the consistency ?</p>
  
  <p>Mongo also provides asynchronous replication, which means there will be replication lag b/w master and slave. hence consistency
  can't be promised. So how Mongo says it provides consistency ?</p>
  
  <p><strong>Update :-</strong></p>
  
  <p>As I understand from <a href="https://stackoverflow.com/questions/11292215/where-does-mongodb-stand-in-the-cap-theorem">Where does mongodb stand in the CAP theorem?</a> is that Mongo provides consistency
  when system is is a single-master system and all reads go to the primary by default.</p>
  
  <p>But When optionally enable to read from the secondaries then MongoDB becomes eventually consistent where it's possible to read out-of-date results.
  So there is possiblity that Mongo system is inconsistent in betweena and does not provide the latest written data.</p>