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Route53 Routing Policies

Links: 101 AWS SAA Index

  • Routing policies define how Route53 should respond to DNS queries.
    • It doesn't route any traffic it just responds to DNS queries in a specific way depending on the policy.
All routing policies have health checks except simple.

Simple

  • It will route traffic to a single resource.
  • We can specify multiple values in the same record.
    • If multiple values are returned then a random one is chosen by the client.
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  • It cannot be associated with health checks
  • When ALIAS is enabled it can point to only 1 AWS resource.

Multi value

  • It is used when you want to route traffic to multiple resources
  • Can be associated with health checks (return only values with positive health checks)
  • Multi value is NOT a substitute for ELB.
    • It is client side load balancing.
  • Upto to 8 healthy records are returned by each multi value query.
  • It is a better version of simple type since it only returns the IPs which are healthy.

Weighted

  • Control the % of request that go to each resource.
  • Each record is assigned a relative weight
  • The weights need not sum to 100.
  • We can associate them with health checks.
  • Assigning a weight of 0 means we will stop sending traffic to that particular resource.
  • Whereas if all records have a weight of 0 then all the records will be returned equally.
  • Use case would be to load balance between different regions or test the new application version.
  • We also use weighted routing for active active failover and active passive failover.

Latency based

  • Redirect to resource which has the lowest latency.
Useful when latency for users is a priority.
  • Latency is based on traffic between users and AWS regions.
  • Germany users may be redirected to resource in US if it has the lowest latency.
  • It can be combined with health checks.
If you see terms like latency, high load times, deteriorated performance then always go for latency based routing.

You can use geolocation routing to restrict the distribution of content to only the locations in which you have distribution rights. You cannot use geolocation routing to reduce latency even though you might think it makes sense to serve US users from US region.

If your application is deployed in only a single region and you want to reduce latency then Latency based routing will be of no use.

Failover

  • Health check is mandatory.
  • We need 2 different records: a primary record and a secondary record.
  • DNS failover to a standby instance
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Active Active Failover

  • Use this failover configuration when you want all of your resources to be available the majority of the time.

Active Passive Failover

  • Use an active-passive failover configuration when you want a primary resource or group of resources to be available the majority of the time and you want a secondary resource or group of resources to be on standby in case all the primary resources become unavailable.

Geolocation

  • Routing is based on user location.
  • There should be a default record if there is no match on location.
  • Use cases would be website localisation (NETFLIX), restrict content distribution, load balancing etc
  • It can be associated with health checks.
  • We can specify location by
    • country
    • continent
    • US state
Mainly for content restriction, distribution rights.

Geoproximity

  • Route traffic to resources based on the geographic location of users and the resources
  • We can shift more traffic to resources based on bias.
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  • We must use Route 53 Traffic Flow (advanced) to use this feature.
    • We can setup very advanced rules.
    • Traffic Flow supports versioning.
    • It will be saved as traffic flow policies.
  • It is really helpful if we need to shift the traffic from one region to another by changing the bias.
Trick question to confuse between Geolocation and Geoproximity

A company runs a messaging application in the ap-northeast-1 and ap-southeast-2 region. A Solutions Architect needs to create a routing policy wherein a larger portion of traffic from the Philippines and North India will be routed to the resource in the ap-northeast-1 region.

We are not specifying complete countries but only a portion. This is a perfect use case of bias hence geoproximity.

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  • Use Geoproximity if you want to route based on the location of resources.

Last updated: 2023-03-13