If it is at all a decent system most boards that control the door locks have battery backups for this situation. Our keyfob/door lock system at our small offic

If it is at all a decent system most boards that control the door locks have battery backups for this situation. Our keyfob/door lock system at our small office works in this way where if you were to lose power the boards still operate on their own independent system via battery power up to 48 hours with no power. Even on a server controlled system the server client only issues updates to names/keyfobs on the control boards and even if the server computer were to go down any current information still works as intended with no power and the boards operating on battery (which most last 48 hours and the batteries are cheap to replace so unless it is an extended outage you are fine)