Start with a high-level overview of DNS as the internet's distributed directory service, then walk through the resolution process from a client's perspective. Emphasize the hierarchical and distributed nature of DNS, and connect it to scalability, caching, and trade-offs relevant to system design at Amazon.
Pro tip: Mention how DNS caching and TTLs affect system design, and relate it to real-world scenarios like failover, load balancing, and latency optimization—showing you understand operational implications beyond just the protocol.
Explain that DNS translates human-readable domain names into IP addresses, acting as the internet's phonebook. Highlight its distributed, hierarchical design for scalability and fault tolerance.
Outline the tree structure: root servers, top-level domain (TLD) servers, and authoritative name servers. Mention that each level delegates responsibility, enabling distributed management.
Detail a typical query: client checks local cache, then queries recursive resolver, which iteratively queries root, TLD, and authoritative servers. Explain caching at each step to reduce latency.
Mention common DNS record types (A, AAAA, CNAME, MX, NS, TXT) and their purposes. Connect to system design, e.g., using CNAME for load balancing or A records for IP mapping.
Discuss trade-offs like TTL vs. consistency, caching vs. freshness, and DNS as a point of failure. Relate to Amazon-scale systems: latency, failover, and global traffic management.
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