Zookie is an opaque cookie passed to and from the Authzed API to ensure that permissions are not stale when checked against specific objects.
A Zookie is necessary for Authzed to ensure that the New Enemy Problem cannot occur.
Zookies also allow Authzed to optimize the lookup of permissions: if the relations or objects have not changed in some time and by knowing that we have the sufficiently fresh copy of the permissions in a local cache, Authzed can use the cache rather than fetching from another node.
It is generally recommend to store the Zookie returned by
Write next to the object in your own database, and then to give it back to the Authzed API on all
Expand calls for that object.