If using memcached with
Keystone - e.g. using the memcache token driver or the
auth_token middleware - ensure that the system
time of memcached hosts is set to UTC. Memcached uses the host's
system time in determining whether a key has expired, whereas
Keystone sets key expiry in UTC. The timezone used by Keystone and
memcached must match if key expiry is to behave as expected.
