zone

Defines the name and size of the shared memory zone that keeps the group’s configuration and run-time state that are shared between worker processes. Several groups may share the same zone. In this case, it is enough to specify the zone size only once.

Additionally, as part of our commercial subscription, such groups allow changing the group membership or modifying the settings of a particular server without the need of restarting nginx. The configuration is accessible via a special location handled by upstream_conf.