How Twitter DDoS’d our Website 61 times in Past 2 days

in short, twitter didn't DDoS them, it was the result of all the various bots that look for new urls posted to twitter and fetch them for whatever reason.

the article says the "DDos" was "80 requests within the span of 2-3 seconds". if that amount of traffic causes as much trouble to your server as it did for that site (load average of 31, out of swap memory, server reboots), you have a really shitty architecture.

it sounds like twitter did these guys a favor by pointing out how poorly engineered their site was. why they posted about it and drew attention to their problem, i have no idea.

You shouldn't be getting DDoS'd by a bunch of bots. Since you're using Apache with that hardware, you should be able to avoid crashing the entire server. Regardless, you should be able to control your server enough to avoid having it swap/crash. May want to hire a sysadmin with more experience.

I'm not familiar with the interals of WP Super Cache, but it is really odd that a cached page can't be served ~80 req/s. Perhaps Varnish will work in the case where WP Super Cache can't be tooled to write-through to cache or sooner.

"How I Run a Website with Swap On"