To follow this up: test these situations, design yourself into resilience. obviously, you can't build perfection in a day, but for anything you rely on, be it

To follow this up: test these situations, design yourself into resilience. obviously, you can't build perfection in a day, but for anything you rely on, be it mysql, redis, memcached, postgresql, rabbitmq, whatever, just kill -9 that shit in staging periodically while a few people hit the url, and see what happens, what logs, etc.. assume failure.