Generally described, the present disclosure is directed to managing request routing functionality corresponding to resource requests for one or more resources associated with a content provider. The processing of the DNS requests by the service provider can include the selective filtering of DNS queries associated with a DNS query-based attack. A service provider can assign DNS servers corresponding to a distributed set of network addresses, or portions of network addresses, such that DNS queries exceeding a threshold, such as in DNS query-based attacks, can be filtered in a manner that can mitigate performance impact on for the content provider or service provider.