RubyDNS is a high-performance DNS server that can be easily integrated into other projects or used as a stand-alone daemon (via RExec). By default, it uses rule-based pattern matching. Results can be hard-coded, computed, fetched from a remote DNS server, or fetched from a local cache, depending on requirements. In addition, RubyDNS includes a high-performance asynchronous DNS resolver built on top of EventMachine. This module can be used by itself in client applications without using the full RubyDNS server stack.