The engineering questions you get asked, and the bugs you actually hit. Drawn, one mechanism at a time, in the order the videos ship.
Why naive modulo hashing causes catastrophic cache stampedes when resizing clusters, and how the 360-degree hash ring bounds key remapping to K/N.
You changed the price an hour ago and somebody just paid the old one. HTTP gives a server exactly one way to remove something from a cache, and it is a side effect rather than a command.
The page said welcome back, with somebody else's name on it. Four questions decide whether something in the path may answer instead of your server — and the default, when you say nothing at all, is not 'don't cache'.
You asked for a name and a price and thirty-eight fields came back. Every difference between the two is one trade seen from a different side — and the caching bill is where it comes due.
A CDN is not a faster server. It's a copy of your response nearer the person asking — and everything that surprises you about it follows from what HTTP lets a shared cache keep.
