1. A method, comprising: maintaining, by one or more servers of a computer data center, a plurality of instances of a database system, wherein each of the plurality of instances is associated with a plurality of tenants and is separately configured to provide functionality of the database system to the associated plurality of tenants; receiving, by the one or more servers from a first user associated with one of the plurality of tenants, a first request to create a custom subdomain within a domain of the one or more servers; in response to receiving the first request, the one or more servers: creating the custom subdomain within the domain of the one or more servers; and associating the custom subdomain with an instance of the plurality of instances capable of executing an application of the tenant; receiving, by the one or more servers from a second user, a second request for content from the application of the tenant, wherein the second request specifies the custom subdomain; and in response to receiving the second request, the one or more servers: determining the instance from the plurality of instances based on the custom subdomain; and routing the second request to the application executing on the instance.