Tutorials System Design Tutorial
DNS for System Design — Complete Guide
DNS for System Design — Complete Guide: free step-by-step lesson with examples, common mistakes, and interview tips — part of System Design Tutorial on Toolliyo Academy.
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System Design Tutorial · Lesson 11 of 100
DNS for System Design
Basics → Scale → Interview
Basics · 1 — Building blocks · ~6 min · Module 2: Networking and Traffic Management
What is this?
DNS maps names like api.shopnest.com to addresses and can steer traffic across regions with TTLs and records (A/AAAA/CNAME).
Why should you care?
Before load balancers, clients must find ShopNest. DNS is the first routing layer and a failover tool.
See it live — copy this example
Sketch the architecture on paper. These lessons focus on concepts and trade-offs.
api.shopnest.com → CNAME → shopnest-lb-prod.example
TTL 60s during failover drills
www.shopnest.com → CDN
geo DNS (optional): IN → Mumbai LB, US → Virginia LBRun Example »
This lesson uses terminal or setup steps. Run commands on your computer — the live editor appears on coding lessons.
What happened?
- Low TTL helps failover but increases DNS lookups.
- CDN hostnames often sit in front of static assets.
- API names point at load balancers.
Practice next
- Write DNS records for www and api.
- Pick a TTL for normal vs incident mode.
- Explain why changing DNS alone is not instant.
- Sketch failover by switching CNAME targets.
- Add a health-checked traffic-manager record (conceptually).
Remember
DNS names the entry points. TTL trades cache vs agility. Use DNS with LB/CDN, not instead of health checks.
api.shopnest.com cutover
Ops lowers TTL then swings CNAME to a new LB.
Outcome: Clients converge to the healthy entry point.
Interview prep for this lesson
Practice these questions aloud after reading—each links to a full structured answer.
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