AWS Route 53 Interview Questions
Core Concepts
Q: Routing policies.
•Simple: Standard DNS, one or more values
•Weighted: Split traffic by % (A/B testing, canary)
•Latency: Route to lowest-latency region for user
•Failover: Primary + secondary, failover when health check fails
•Geolocation: Route by user's country/continent (compliance, language)
•Multi-value: Return multiple healthy IPs
Q: Health checks.
bash
aws route53 create-health-check \
--health-check-config '{
"Type": "HTTPS",
"FullyQualifiedDomainName": "api.example.com",
"ResourcePath": "/health",
"RequestInterval": 30,
"FailureThreshold": 3
}'
Types: endpoint (HTTP/HTTPS/TCP), CloudWatch alarm, calculated (combine multiple).
Q: Alias vs CNAME.
|---|---|---|
| Zone apex | NO (example.com fails) | YES |
|---|
| AWS targets | Standard resolution | Auto-follows IP changes |
| Cost | Charged per query | Free for AWS resources |
yaml
# Always use Alias for ALB, NLB, CloudFront, S3, API GW
# CNAME only for external non-AWS hostnames
Q: Private hosted zones.
DNS resolution within VPC only — not resolvable from internet.
bash
aws route53 create-hosted-zone \
--name internal.company.com \
--vpc VPCRegion=us-east-1,VPCId=vpc-xxx
# database.internal.company.com -> 10.0.5.100 (private RDS)
Use for: service discovery, database/cache endpoints, microservice-to-microservice.
Revision Notes
ROUTING POLICIES:
Simple: one record | Weighted: % split (A/B test)
Latency: closest region | Failover: primary/secondary
Geolocation: by country | Multi-value: multiple healthy IPs
HEALTH CHECKS:
Endpoint (HTTP/TCP) | CloudWatch alarm | Calculated (combine checks)
3 consecutive failures -> unhealthy -> failover activates
ALIAS vs CNAME:
Alias: works at zone apex, free for AWS resources, auto-follows IP changes
CNAME: not at apex, charged, for external hostnames
Use Alias for: ALB, NLB, CloudFront, S3, API GW
PRIVATE ZONES: VPC-only DNS. Service discovery. DB endpoints.
