DNS was created in 1983. Before then, Stanford was storing the host name to IP address map on HOSTS.TXT, which obviously doesn’t scale. DNS is the address book of the internet, which performs a simple function of translating domains to IP addresses. One way of looking at it is that it’s a distributed read-heavy database with caches on top. Just like the internet is probably the first distributed system at large, DNS is probably the first distributed database ever — if you think about DNS as a whole that stores this lookup map and serves reads & writes operations to this map.