systemd-localed is a system service that may be used as mechanism to change the system locale settings, as well as the console key mapping and default X11 key mapping. systemd-localed is automatically activated on request and terminates itself when it is unused.
The tool localectl(1) is a command line client to this service.
See the developer documentation  for information about the APIs systemd-localed provides.
systemd(1), locale.conf(5), vconsole.conf(5), localectl(1), loadkeys(1)