get node id from entityQuery('node')

I want to get the node id from entityQuery('node') the below query give me array vid = nid

$nids = \Drupal::entityQuery('node')
->condition('status', 1)
->condition('type', 'account_content')
->condition('field_account_id', $accountid)
->execute();

When using array_keys($nids) // getting vid which is revision id

When using array_values($nids) // getting nid which is node id

I want the node id i.e. nid rather to vid

$nids['nid'] = numeric value nid

because am not sure whether i am getting $nids = array([1] => [1]) array key is nid or vid same for value

You should check the method comments about the return value in the Drupal/Core/Entity/Query/QueryInterface::execute() https://api.drupal.org/api/drupal/core%21lib%21Drupal%21Core%21Entity%21Query%21QueryInterface.php/function/QueryInterface%3A%3Aexecute/9

 /**
   * Execute the query.
   *
   * @return int|array
   *   Returns an integer for count queries or an array of ids. The values of
   *   the array are always entity ids. The keys will be revision ids if the
   *   entity supports revision and entity ids if not.
   */

So, it give you an array, get the keys or values depends on your need.

You can create an array keyed by NID, with the value being the NID as follows:

$nids = \Drupal::entityQuery('node')
  ->condition('status', 1)
  ->condition('type', 'account_content')
  ->condition('field_account_id', $accountid)
  ->execute();

// Create an array, each element of which
// is keyed by the NID, with the value being
// the NID.
$nids = array_combine($nids, $nids);

If the values explicitly need to be integers you can run through the resultant array:

// Cast the value of each element of the array
// as an integer, by walking through each element
// of the array.
array_walk($nids, function(&$value) {
  // Cast the value as an integer.
  $value = (int) $value;
});