AWS Route 53 Routing Policies Comparison

• Amazon Route 53 supports 7 routing policies that determine how DNS queries are answered.
• Choosing the right routing policy depends on whether you need failover, latency optimization, geographic restrictions, or traffic distribution.
• Multiple policies can be combined using alias records and health checks for complex routing architectures.

Route 53 Routing Policies Comparison

Simple Routing

• Routes traffic to a single resource (or multiple values returned in random order).
• Cannot attach health checks to simple routing records.
• If multiple values are returned, client chooses one randomly (client-side load balancing).
• Can only have one record per name with simple routing.
• Best for: Single server, single resource behind a load balancer.

Weighted Routing

• Routes traffic based on weights assigned to records (0-255).
• Traffic proportion = record weight / sum of all weights for the same name.
• Setting weight to 0 stops traffic to that resource (useful for maintenance).
• If all records have weight 0, traffic is distributed equally.
• Supports health checks – unhealthy records removed from responses.
• Best for: Blue/green deployments (90/10 split), A/B testing, gradual migrations, load distribution across regions.

Latency-based Routing

• Routes traffic to the region with the lowest network latency for the user.
• Latency is measured between the user’s DNS resolver and AWS regions.
• Requires resources in multiple AWS regions.
• Supports health checks – if lowest-latency resource is unhealthy, routes to next-best.
• Latency data is updated periodically by AWS (not real-time per request).
• Best for: Global applications deployed in multiple regions needing best user experience.

Failover Routing

• Routes traffic to primary resource when healthy, secondary when primary fails health check.
• Active-passive configuration – only one designation per record set (primary or secondary).
• Health check required on primary record; optional on secondary.
• Secondary can point to a static S3 website (maintenance page) or another resource.
• Can be combined with other routing policies using alias records.
• Best for: Disaster recovery, maintenance pages, active-passive HA architectures.

Geolocation Routing

• Routes traffic based on geographic location of the user (continent, country, or US state).
• Most specific match wins – state > country > continent > default.
• A default record is recommended – users from unmapped locations get this response.
• If no default and no match, Route 53 returns “no answer”.
• Does NOT route to closest resource – routes to the location you configure (use geoproximity for nearest).
• Best for: Content localization (language), compliance (restrict access by country), serving region-specific content.

Geoproximity Routing

• Routes traffic based on geographic distance between user and resources.
• Bias values (-99 to +99) expand or shrink the geographic area that routes to a resource.
• Positive bias = attracts more traffic (expands coverage area).
• Negative bias = repels traffic (shrinks coverage area).
• Supports both AWS resources (auto-detects region) and non-AWS resources (specify latitude/longitude).
• Requires Route 53 Traffic Flow to use geoproximity routing.
• Best for: Routing to nearest resource with ability to shift traffic between regions using bias.

Multivalue Answer Routing

• Returns up to 8 healthy records in response to each DNS query.
• Similar to simple routing but supports health checks – only healthy resources returned.
• Not a substitute for a load balancer but provides basic DNS-level load balancing with health checking.
• Each record can have its own health check.
• Best for: Basic load distribution with health checking when you don’t need ELB.

IP-based Routing

• Routes traffic based on client’s source IP address mapped to CIDR blocks.
• Create CIDR collections with locations, then map records to locations.
• Useful when you know the IP ranges of your users (corporate networks, ISPs).
• More precise than geolocation – routes based on actual network, not estimated location.
• Best for: ISP-specific routing, enterprise users with known IP ranges, optimizing costs by routing to specific endpoints.

Combining Routing Policies

• Alias records can point to other Route 53 record sets, enabling policy combinations.
• Example: Latency → Weighted (route to nearest region, then split between blue/green within region).
• Example: Failover → Latency (primary is latency-based across regions, secondary is S3 static page).
• Example: Geolocation → Failover (per-country routing with DR fallback).
• Traffic Flow – visual editor for building complex routing trees with multiple policies.

AWS Certification Exam Practice Questions

1. A company wants to gradually migrate traffic from an on-premises data center to AWS by sending 10% of traffic to AWS initially, increasing over time. Which routing policy supports this?
   1. Latency-based
   2. Weighted
   3. Failover
   4. Geolocation
2. An application deployed in us-east-1 and eu-west-1 should route users to whichever region provides the fastest response. Which routing policy is appropriate?
   1. Geolocation
   2. Geoproximity
   3. Latency-based
   4. Weighted (50/50)
3. A streaming service must serve different content libraries to users in different countries due to licensing restrictions. Which routing policy enforces this?
   1. Latency-based
   2. Geolocation
   3. Geoproximity
   4. IP-based
4. A company needs to route traffic to the nearest data center but temporarily shift more traffic to a new region during a migration. Which routing policy allows adjusting the geographic coverage area?
   1. Geolocation with failover
   2. Weighted with latency
   3. Geoproximity with bias
   4. Multivalue answer
5. An architect needs DNS-level health checking where unhealthy endpoints are automatically removed from DNS responses, but a full load balancer is not required. Which policy provides this with multiple IPs?
   1. Simple routing
   2. Weighted routing
   3. Failover routing
   4. Multivalue answer routing

Related Posts

• AWS Route 53
• AWS Route 53 Alias vs CNAME
• AWS CloudFront vs Global Accelerator
• AWS High Availability & Fault Tolerance Architecture

References

Route 53 Routing Policies

Route 53 Traffic Flow