Every Friday at four

The mistake

The load-test script that fires a million simulated shoppers is pointed at the production endpoint instead of a staging/test environment, so it hits the live shop and blocks real traffic instead of just measuring capacity. Worse, the script (written in 2019) only implements a start routine with no stop, cancel, or kill-switch, so once it's running there is no way to halt the load short of physically cutting its network connection and waiting out the fixed run duration.