Laravel Emails Queue are not stopping or Running Automatically

[sajidfrommerqata]

I'm queuing emails and send them in the background by using PHP artisan queue: work. I'm using AWS Lightsail Linux Instance as Hosting and supervisor for running this command in the background

But I faced a very strange issue. The issue is MYSQL consumes all the memory randomly and bursts the CPU. Then I thought this because of Supervisor. So, I stopped the supervisor by running this command. Sudo /etc/init.d/supervisor stop. The output of this command is [ ok ] Stopping supervisor (via systemctl): supervisor.service.

After supervisor, I used crontab. and then I found the same MySQL issue with crontab also. Then I disabled crontab also by running sudo /etc/init.d/cron stop. The output of the command is [ ok ] Stopping cron (via systemctl): cron.service.

Let me clear one thing here, that I'm testing my application and MySQL is almost empty. Below are the specifications of my virtual machine:

4 GB RAM, 2 vCPUs, 80 GB SSD
LAMP (PHP 7)
Singapore, Zone A (ap-southeast-1a)

So, my question is how emails are sending automatically and why MYSQL burst the CPU?