Laravel taking 100% MySQL DB CPU and no jobs visible in php artisan queue:listen, Laravel 5.7

The MySQL DB CPU is running at 95%+ basically at all times, even when there's seemingly no activity in the app. It doesn't happen right away. Only once the app has been running for a while, but then it keeps at 95% CPU even once there's seemingly no activity.

The number of active sessions / connections gradually climbs from dozens to even hundreds. Looking at the MySQL processes on RDS reveals a dozen processes trying to use 8% of the DB CPU each for some reason.

I've checked for Laravel jobs via php artisan queue:listen but nothing appears.

Checked the database and query logs, and there are many DB logs which suggest a job or something occurring in a loop, but no indication as to what the source of those jobs are as the queries being ran are generic queries and could be called from many different places in the application.

We do not believe this is due to user activity, but if it is, it's some kind of user action whicih results in some kind of a server loop.

Checked application and error logs and nothing in particular stands out.

via Chebli Mohamed