Route 53

Route 53 supports all standard DNS record types and adds a proprietary Alias record type that eliminates the need for CNAME at zone apex (root domain).

Route 53 routing policies control which record values are returned to DNS queries. They can be combined with health checks for automatic failover.

Route 53 health checks monitor endpoints and can automatically remove unhealthy records from DNS responses. They work across all routing policies.

For resources in private VPCs, Route 53 health checkers cannot reach them directly because they operate from public IP ranges. Use a CloudWatch alarm health check instead - create a CloudWatch alarm on a metric (e.g., ALB HealthyHostCount), then link the Route 53 health check to that alarm.

# Create a health check for an HTTP endpoint
aws route53 create-health-check \
  --caller-reference 2024-01-01 \
  --health-check-config \
  "Type=HTTP,FullyQualifiedDomainName=api.example.com,Port=80,RequestInterval=30,FailureThreshold=3"

# Create a failover record set (primary)
aws route53 change-resource-record-sets \
  --hosted-zone-id Z1234 \
  --change-batch '{
    "Changes": [{
      "Action": "CREATE",
      "ResourceRecordSet": {
        "Name": "api.example.com",
        "Type": "A",
        "Failover": "PRIMARY",
        "HealthCheckId": "abc-123",
        "AliasTarget": {
          "DNSName": "my-alb.us-east-1.elb.amazonaws.com",
          "EvaluateTargetHealth": true,
          "HostedZoneId": "ZALBHOSTEDZONEID"
        }
      }
    }]
  }'

Private hosted zones let you resolve custom domain names within VPCs without exposing them to the internet. They are essential for service discovery in multi-VPC architectures.

For on-premises DNS resolution of Route 53 private zones, use Route 53 Resolver endpoints. An inbound endpoint allows on-premises DNS servers to forward queries to Route 53. An outbound endpoint lets Route 53 forward queries for on-premises domains to your on-premises DNS.