QueueWorker in Drupal 8

mymodule.module

<?php
/**
 * Implements hook_entity_update().
 */
function mymodule_entity_update($entity) {
  $queue = \Drupal::queue('mymodule_tasks_entity_updates');
  $data = [ 'entity_type' => $entity->getEntityType(), 'id' => $entity->id()]; 
  $queue->createItem($data);
}

MyModuleTaskWorkerEntityUpdate.php

<?php

/**
 * @file
 * Contains \Drupal\mymodule\Plugin\QueueWorker\MyModuleTaskWorkerEntityUpdate.
 */

namespace Drupal\mymodule\Plugin\QueueWorker;

use Drupal\Core\Queue\QueueWorkerBase;

/**
 * Processes Tasks for My Module.
 *
 * @QueueWorker(
 *   id = "mymodule_tasks_entity_updates",
 *   title = @Translation("My Module Tasks Worker: Entity Updates"),
 *   cron = {"time" = 60}
 * )
 */
class MyModuleTaskWorkerEntityUpdate extends QueueWorkerBase {

  /**
   * {@inheritdoc}
   */
  public function processItem($data) {
    // Process $data here.
  }

}