In the days of Apache 1.3 in the early 2000s for example every client session had a memory footprint (and in the case of php processes could be in the 1-2 megab

In the days of Apache 1.3 in the early 2000s for example every client session had a memory footprint (and in the case of php processes could be in the 1-2 megabytes easy). So there you are on a dedicated piece of hardware with limited RAM and a 10,000 connections hit you at the same time. And you have no caching strategy because you're an idiot child trying your best. Boom - Slashdotted