Checkout Submit Event Observer, huge delays while loading

Question

I am trying to use an Event Observer to run some code after the user checks out. This is what i have so far:

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Event/etc/events.xsd">

   <event name="checkout_submit_all_after">
       <observer name="vendor_module_observer_oncheckout" instance="vendor\module\Observer\Oncheckout" />
   </event>

</config>

This is the Observer File:

<?php
namespace vendor\module\Observer;

class Oncheckout implements \Magento\Framework\Event\ObserverInterface
{

  public $_observer;
  public function execute(\Magento\Framework\Event\Observer $observer)
  {
     $order = $observer->getOrder();
     $orderid = $order->getId();

     //adds $orderid to the database

  }

}

From some research i have done, this is the correct code, and it does work successfully. However, it takes over 1 minute for the code to finish executing and redirect the user to the checkout success page.

What am i doing wrong that causes such a long delay? Without this code, the checkout success page loads up in seconds.

Thanks.

EDIT:

With some investigation, I have found that the module causes the payment-information post request to remain in the pending state for 2.1 minutes

after further testing, the time in the pending state is consistently 2.1 minutes every time