Knot DNS is an open-source authoritative-only server for the Domain Name System. It was created from scratch and is actively developed by CZ.NIC, the .CZ domain registry. The purpose of this project is to supply an alternative open-source implementation of an authoritative DNS server suitable for TLD operators to increase overall security, stability and resiliency of the Domain Name System. It is implemented as a multi-threaded daemon, using a number of programming techniques and data structures to make the server very fast, notably Read-copy-update or a special kind of a radix tree.