title: mongo 3 duplicates on unique index - dropDups
body: <p>In the documentation for mongoDB it says:
  "Changed in version 3.0: The dropDups option is no longer available."</p>
  
  <p>Is there anything I can do (other than downgrading) if I actually want to create a unique index and destroy duplicate entries?</p>
  
  <p>please keep in mind the I receive about 300 inserts per second so I can't just delete all duplicates and hope none will come in by the time I'm done indexing. </p>