AWS for DevOps — Route 53

12.1 — Route 53

Route 53 is AWS’s DNS service. It translates domain names (like api.example.com) to IP addresses or AWS resources. For DevOps, it’s critical for blue-green deployments, failover, and traffic management.

Real-World Analogy

Route 53 is like a phone directory for the internet. When someone dials “api.example.com,” Route 53 looks up the number (IP address) and connects the call. It can also route calls based on the caller’s location, or switch calls to a backup number if the primary is down.

Record Types

Type	Purpose	Example
A	Domain → IPv4 address	api.example.com → 54.12.34.56
AAAA	Domain → IPv6 address	api.example.com → 2001:db8::1
CNAME	Domain → another domain	www.example.com → example.com
Alias	Domain → AWS resource (free, zone apex)	example.com → ALB DNS name
MX	Mail server routing	example.com → mail.example.com
TXT	Text records (verification, SPF)	example.com → "v=spf1 ..."

Creating a Hosted Zone

# Create a public hosted zone
$ aws route53 create-hosted-zone \
    --name example.com \
    --caller-reference "$(date +%s)"
{
    "HostedZone": {
        "Id": "/hostedzone/Z1234567890",
        "Name": "example.com.",
        "ResourceRecordSetCount": 2
    },
    "DelegationSet": {
        "NameServers": [
            "ns-1234.awsdns-12.org",
            "ns-567.awsdns-34.com",
            "ns-890.awsdns-56.co.uk",
            "ns-123.awsdns-78.net"
        ]
    }
}

Creating Records

# Create an A record pointing to an EC2 instance
$ aws route53 change-resource-record-sets \
    --hosted-zone-id Z1234567890 \
    --change-batch '{
      "Changes": [{
        "Action": "CREATE",
        "ResourceRecordSet": {
          "Name": "api.example.com",
          "Type": "A",
          "TTL": 300,
          "ResourceRecords": [{"Value": "54.12.34.56"}]
        }
      }]
    }'

# Create an Alias record pointing to an ALB
$ aws route53 change-resource-record-sets \
    --hosted-zone-id Z1234567890 \
    --change-batch '{
      "Changes": [{
        "Action": "CREATE",
        "ResourceRecordSet": {
          "Name": "api.example.com",
          "Type": "A",
          "AliasTarget": {
            "HostedZoneId": "Z35SXDOTRQ7X7K",
            "DNSName": "my-alb-123456.ap-south-1.elb.amazonaws.com",
            "EvaluateTargetHealth": true
          }
        }
      }]
    }'

Routing Policies

Policy	Use Case	How It Works
Simple	Single resource	Returns one value
Weighted	A/B testing, gradual migration	90% to v1, 10% to v2
Latency	Multi-region apps	Routes to lowest latency region
Failover	Disaster recovery	Primary → Secondary on health check failure
Geolocation	Compliance, localization	Route by user’s country/continent

Weighted Routing (Blue-Green)

# Send 90% to blue (current), 10% to green (new)
$ aws route53 change-resource-record-sets \
    --hosted-zone-id Z1234567890 \
    --change-batch '{
      "Changes": [
        {
          "Action": "CREATE",
          "ResourceRecordSet": {
            "Name": "api.example.com",
            "Type": "A",
            "SetIdentifier": "blue",
            "Weight": 90,
            "AliasTarget": {
              "HostedZoneId": "Z35SXDOTRQ7X7K",
              "DNSName": "blue-alb.ap-south-1.elb.amazonaws.com",
              "EvaluateTargetHealth": true
            }
          }
        },
        {
          "Action": "CREATE",
          "ResourceRecordSet": {
            "Name": "api.example.com",
            "Type": "A",
            "SetIdentifier": "green",
            "Weight": 10,
            "AliasTarget": {
              "HostedZoneId": "Z35SXDOTRQ7X7K",
              "DNSName": "green-alb.ap-south-1.elb.amazonaws.com",
              "EvaluateTargetHealth": true
            }
          }
        }
      ]
    }'

Health Checks

# Create a health check for your API
$ aws route53 create-health-check \
    --caller-reference "$(date +%s)" \
    --health-check-config '{
      "IPAddress": "54.12.34.56",
      "Port": 443,
      "Type": "HTTPS",
      "ResourcePath": "/health",
      "RequestInterval": 30,
      "FailureThreshold": 3
    }'

Common Mistakes

Mistake	Why It Hurts	Fix
Using CNAME at zone apex	DNS spec doesn’t allow it	Use Alias records (free, works at apex)
High TTL during migration	Slow failover, stale DNS	Lower TTL to 60s before changes, raise after
No health checks on failover records	Failover doesn’t work	Always attach health checks to failover records
Forgetting to update name servers at registrar	Domain doesn’t resolve	Copy NS records from Route 53 to your registrar

Quick Reference

Task	Command
Create hosted zone	aws route53 create-hosted-zone --name DOMAIN --caller-reference REF
Create/update record	aws route53 change-resource-record-sets --hosted-zone-id ID --change-batch '...'
List records	aws route53 list-resource-record-sets --hosted-zone-id ID
Create health check	aws route53 create-health-check --caller-reference REF --health-check-config '...'
Test DNS resolution	dig api.example.com or nslookup api.example.com

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