irb(main):046:0> User.where({}).max_scan(1).to_a().length
=> 4326
irb(main):047:0> User.where({}).max_scan(1).explain
=> {"cursor"=>"BasicCursor", "isMultiKey"=>false, "n"=>4326, "nscannedObjects"=>4326, "nscanned"=>4326, "nscannedObjectsAllPlans"=>4326, "nscannedAllPlans"=>4326, "scanAndOrder"=>false, "indexOnly"=>false, "nYields"=>0, "nChunkSkips"=>0, "millis"=>1, "indexBounds"=>{}, "allPlans"=>[{"cursor"=>"BasicCursor", "n"=>4326, "nscannedObjects"=>4326, "nscanned"=>4326, "indexBounds"=>{}}], "server"=>"jon.local:27017"}