Changing to ElggBatch will not make the process consume less CPU it'll go as fast as it can thus using all CPU.

If you want it to slow down build in a sleep(). Bu then it'll take longer.

Also with ElggBatch make sure 'limit' is set to false.

Also if your calling your cron job with curl you'll get the overhead of the webserver. Just make a script which does this part

// start Elgg (in pseudo code)
- Load the Composer autoloader
- start the Elgg Application

// start removing your entities
$options = [
    'type' => 'object', 
    'subtype' => 'subtype_needed_to_be_deleted', 
    'limit' => false,
    'batch' => true,
    'batch_inc_offset' => false,
];

$entities = elgg_get_entities($options);

foreach ($entities as $entity) {
   echo "Removing GUID: {$entity->guid}" . PHP_EOL;
   ...deletion process---
}

The foreach loop will go on until all entities have been removed

Thanks Jerome! I will try your recommendation and let you know how it goes.

With your approach, the CPU usage is mostly below 50% for MySQL service. Awesome!!

Thanks again Jerome!