Amazon Route 53 DNS Design - Routing Policies and Health Checks in Practice
Achieve advanced traffic control with alias records and seven routing policies. This article covers multi-region failover design using health checks.
Route 53 Basics and Alias Records
Route 53 is an authoritative DNS service provided by AWS that integrates three functions: domain registration, DNS routing, and health checks. Its standout feature is the alias record. Standard DNS does not allow CNAME records at the Zone Apex (a naked domain like example.com), but Route 53 alias records bypass this limitation, letting you map AWS resources such as CloudFront distributions, ALBs, and S3 static website endpoints directly to the Zone Apex. DNS queries to alias records are free, and no additional DNS resolution occurs as with CNAMEs, making alias records advantageous in both latency and cost.
Choosing the Right Routing Policy
Route 53 offers seven routing policies. Simple routing directs traffic to a single resource. Weighted routing distributes traffic across multiple resources by proportion, useful for canary releases where you send 10% of traffic to a new version. Latency-based routing automatically selects the lowest-latency region for each user. For an application deployed in Tokyo and Virginia, Japanese users are routed to the Tokyo region while US users are routed to the Virginia region. Failover routing defines a primary and secondary target and automatically switches over when a health check fails. Geoproximity routing lets you adjust routing ranges with bias values to steer traffic toward specific regions.
Health Checks and Failover Design
Route 53 health checks periodically monitor HTTP/HTTPS/TCP responses from endpoints using health checkers distributed around the world. By default, checks run every 30 seconds, and an endpoint is marked unhealthy after three consecutive failures. Enabling fast health checks (10-second intervals) can reduce failure detection to roughly 10 seconds. In a multi-region failover design, you attach a health check to the primary region's ALB and use failover routing to point to the secondary region's ALB. Health checks can also integrate with CloudWatch alarms, using alarm state as the health check verdict. This enables failover based on custom application metrics, not just endpoint responses. For a deeper dive into Route 53, you can also explore related books on Amazon.
Route 53 Pricing
Route 53 hosted zones cost $0.50 per zone per month. DNS queries are charged at $0.40 per million for the first 1 billion queries per month, and queries to alias records are free. Using alias records for routing to CloudFront and ALB can significantly reduce DNS query costs. Health checks cost $0.50 per check per month for AWS endpoints, and fast health checks (10-second intervals) cost $1.00 per month. There is no additional charge for using latency-based or failover routing.
Summary
Route 53 is a DNS service that handles everything from simple name resolution to advanced traffic control through alias records and versatile routing policies. Combining health checks with failover routing enables highly available multi-region architectures at the DNS layer. Its 100% availability SLA serves as a critical foundation for infrastructure reliability.