m6.12xl are 48 vCPU systems. 25 million cores is a hilariously huge amount of compute to use to run a site of twitter size, which I guess does point to how much tech debt they have ignored over time.
There is nothing simple in data moving. Problem is that it can be abstracted away so you do not have to worry about it. Out of sight out of mind. Example - majority of the CPU area is devoted to data moving problem (cache, branch prediction, out of order execution, register renaming). The same is happening on other levels of the stack (OS, network and so on).
But they do serve videos, which possibly they have to transcode or otherwise process on import (?)
They probably also have some filters for pictures to remove porn and stuff like that.
This can amount to serious CPU if you have millions of users uploading that stuff daily.
