Spectre and Meltdown

A few years passed, but I never really took the time of learning how these
infamous vulnerability work.

I've been pointed to a nice video that explains the whole thing in a very
understandable way: https://www.youtube.com/watch?v=IPhvL3A-e6E

This attack is quite clever.
I might be wrong, but it feels to me somewhat hard to pull off.