MongoDB fast base? Why is everything not so rosy for me?

Question

MongoDB

So! Installed MongoDB. Before rushing into battle and adding real data there, I decided to play a little with the database and what was my surprise when the fetch request took as much as 4 seconds, despite the fact that there were only 3kk (million) test small documents. Maybe I'm doing something wrong? Actually the question is obvious. How to achieve a normal data sampling rate? Below is the code and data with which I tested.

$connection = new MongoClient('192.168.1.102:27017');
$db = $connection->mongo;
$collection = $db->user;
$i = 0;
$this->timer_start();
while($i < 3000000){
$doc = array(
"user_id"=>$i,
"user_name"=>"john_smith",
"first_name"=>"John",
"last_name"=>"Smith",
"phone"=>array(
  "+48576938575773732",
  "+23423429384239489",
  ),
);
$i++;
$collection->insert($doc);
}
echo "Insert in database: ".$this->timer_stop()."<hr>";

$filter = array("user_id"=>999999);
$this->timer_start();
$docs = $collection->find($filter);
echo $docs->count()."<hr>";
print_r($docs->getNext());
echo "<hr>";
echo "Search in database: ".$this->timer_stop()."<hr>"; //4,0992350578308

Answer 1

You are prompted that there are indexes in the monge. One of them is even generated automatically - by the "_id" field. Drop this base, create the same one, but with the replacement "user_id" -> "_id" (initialization of this field is allowed, modification is not), you should like it.
Well, read about indexes - what I will retell you)