TL;DR — DNS System

Design a DNS (Domain Name System) infrastructure that resolves domain names to IP addresses at global scale. The system must support both recursive resolution (client-facing resolvers that walk the DNS tree) and authoritative name servers that hold the actual zone data. DNS is the backbone of the internet -- every HTTP request starts with a DNS lookup. Key features: Recursive resolver: resolve any domain name by walking the DNS hierarchy. Authoritative server: serve zone data for hosted domains with SOA, A, AAAA, CNAME, MX, TXT records.