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.
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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