Indexes
Just like a relational database, mongoDB also benefits from indexes.
Every collection has (automatically) an index on %_id%.
Indexes can be on single or multiple fields.
MongoCursor->explain().
demo->elephpants;
$c->drop();
$c->insert( [ '_id' => 'ele1', 'name' => 'Jumbo' ] );
$c->insert( [ '_id' => 'ele2', 'name' => 'Tantor' ] );
var_dump( $c->find( [ '_id' => 'ele1' ] )->explain() );
?>]]>