Backend
How TCP works: the handshake isn't politeness
Three messages before a byte moves, an ACK that isn't a receipt, and the half a ninety-second video has to cut: how fast to send, how much to hold, and where QUIC takes the whole job away.
How it actually works
The engineering questions you get asked, and the bugs you actually hit. Drawn, one mechanism at a time, in the order the videos ship.