No, they will magically reappear the next time memcached is restarted. The way the article describes the idea the same thing will happen when there is a databas

No, they will magically reappear the next time memcached is restarted. The way the article describes the idea the same thing will happen when there is a database error during user deletion: The user will be gone from the cache, but may reappear later. To make this scheme work, both the database and memcached must be made to support two phase commit, or the application must try to get the shard information from the database if it isn't in the cache.