System design interview questionEasyBasic System Component

Design a DNS System

Design a DNS-like name resolution path: clients resolve a hostname to an address via DNS, then reach edge services.

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Interview scope

Client → DNS → CDN or Load Balancer (or API Gateway). Origin/app may sit behind. No Client → DB.

Functional requirements

Resolve a domain name before connecting to a service.
Route users toward LB/CDN/API edge entry points.
Support many clients asking the same popular names.

Scale and quality goals

Resolution should be fast and highly available.
Clients should not skip DNS and hardcode fragile paths as the only design.
After DNS, traffic still hits LB/CDN — not the DB directly.

Capacity assumption

Design for this scale

Assume ~500M DNS lookups/day (~5,800 RPS average) for a popular zone family.

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