read-operations-only:   is there way have mongodb replica set, make mongodb instance on box connected to, mongodb gets queried?   i have 3 ec2 instances behind aws load balancer.   on each ec2 instance runs mongodb, part of replica set.   i have express endpoints on nodejs , connect replica set follows    mongodb.mongoclient.connect('mongodb://1.1.1.1,2.2.2.2,3.3.3.3.',     function (err, db)     {         if (err)         {             complete('{}');         }         else         {   i distribute load of queries evenly across 3 instances of mongodb replica set instead of default having queries routed ec2 instance primary mongodb defined, because destroys point of load balancer  (which balance load of queries across 3 instances evenly).   my understanding when connecting mongodb replica set,  primary instance selected unless primary instance down, , therefore purpose of every secondary instance serve backup.   in example people call hot,cold,cold.  because there 2...