FFXIV: Endwalker Producer and Director Naoki Yoshida released a message explaining the team’s strategies to prevent Worlds from going down due to server congestion, as well as how it reboots them when they do.
Due to the heavy congestion in FFXIV: Endwalker, Square Enix has also temporarily suspended the renaming service.
In case the World does go down, the FFXIV team essentially troubleshoots what caused it, limits what happened to prevent the crash from happening again, and then reboots the World.
However, if issues persist, the team may further decrease the number of people who can move between areas at once.