Via as-config.yml an admin can configure sharding subdomains for each host or, per default, all hosts. example:

The information is loaded into the users jslob on login. The UI uses this information to distribute image loading requests to the servers supplied. The parameter 'shardingSubdomains' accepts an array of subdomains. If no 'shardingSubdomains' property is provided, the domain name of the user cookies is not set on backend side. Otherwise the given hostname is used.