How customize update interval of aggregator module
The update interval values for an Aggregator Feed is hardcoded into the Entity definition for the refresh field. You'll need to alter the definition to allow different values. 

In a custom module, you can evoke hook_entity_base_field_info_alter() to alter the Feed definition to accept shorter intervals:

function MYMODULE_entity_base_field_info_alter(&amp;$fields, $entity_type) {
  if ($entity_type-&gt;get('id') == 'aggregator_feed') {
    $definition = $fields['refresh']-&gt;getItemDefinition();
    $intervals = $definition-&gt;getSetting('allowed_values');
    $intervals = array(
      120 =&gt; '2 min',
      300 =&gt; '5 min',
      600 =&gt; '10 min',
    ) + $intervals;
    $intervals = $definition-&gt;setSetting('allowed_values', $intervals);
    $fields['refresh']-&gt;setItemDefinition($definition);
  }
}