title: Time taken is changing each time I am executing query in MongoDB
body: <p>I want to check time taken in Milliseconds to execute a query. I am using the command db.collectionname.find().limit(2000).explain(). But each time I run this command it gives different values for Millis for example first time it gives "millis" : 29, second time if I run the same query "millis" : 0 , third time "millis" : 1 and so on. So My question is how to identify how much time it took to execute a mongoDB query and that time should be constant whenever I am executing. What is the significance of Millis in the explain and why is it changing every time.?? Any help is Welcome. Thanks in advance. Regards</p>