DNS Caching Benefits

How DNS caching improves performance in network systems

This is a foundational networking question that tests whether you understand the practical benefits of caching at the DNS layer. It appears in technical interviews for roles involving backend infrastructure, distributed systems, and network optimization, and rewards clear reasoning about latency and load reduction.

To answer well, consider what happens when a resolver must repeatedly look up the same domain: the cost of traversing the DNS hierarchy (root nameserver, TLD nameserver, authoritative nameserver) on every query. Caching eliminates redundant lookups by storing recent responses locally, so subsequent queries return answers from fast memory rather than the network. The question invites you to think about both client-side and server-side caching, TTL (time-to-live) semantics, and the tradeoffs between freshness and speed.

• Hierarchical DNS resolution and the cost of recursive lookups
• TTL (time-to-live) values and cache invalidation
• Reducing load on authoritative nameservers
• Latency reduction for applications and end users