Pit crew
The pit crew is the group of around twenty mechanics who service a car during a stop, each with one job and one only.
Three per corner — one on the gun, one off with the old wheel, one on with the new — plus jack operators, stabilisers and a lollipop or light system controlling the release. A full tyre change is done in around two seconds.
That number is only possible because nobody improvises. Every movement is choreographed and rehearsed, and almost every slow stop traces to one person's step going wrong rather than the whole crew being slow.