Does not actually route or forward traffic (like an ALB) but only responds to queries of a particular domain.
Allows for Public Hosted Zones or Private Hosted Zones.
Contains records with the following attributes:
Name (Domain Name)
Type
Value
TTL
Routing Policy
DNS Record Types
SOA (Start of Authority))
Contains administrative information
NS (Name Server)
Identify the name server and its domain
A record
The IPv4 address of a given host
AAAA
The IPv6 address of a given host
CNAME
Maps one domain name to another
Can’t be used for naked domain
Alias
An AWS extension that points to an AWS resource e.g. CloudFront.
Can be used with naked domain
Does not require TTL
Routing Policies
Simple
It can have multiple values, which will be returned to the client.
The client will choose only one if it receives multiple values
Can only specify one value if it is an alias
No health check.
Weighted
Calculates the portion(percentage) of the traffic by dividing the weight of the record with the combined weight of the same domain.
Can have a health check.
Latency
Choose the lowest latency relative to the client’s location to AWS, so the resource must be in AWS resource.
Must specify the region of the resource. This and the user’s location are used to calculate latency. AWS uses its database to determine the latency of the IP address (https://www.youtube.com/watch?v=PVBC1gb78r8&t=1963s @33:09)
Can have a health check
Failover
Must specify a Primary and Secondary resource.
Traffic is always routed to Primary unless it is not considered healthy. In this case, the Secondary will handle all traffic.
Must always perform health checks.
Geolocation
Route traffic based on where the DNS query originated. Latency is not considered. Can use continent or country or states if in US.
Should have a default record else Route 53 will reply with No Answer.
Can have health check.
Geoproximity
Based on the user and resource location.
By default, returns the endpoint which is of minimal distance from the client.
This can be skewed by changing the bias for a particular location.
Configured from ‘Traffic Policy’.
Multi-value
Similar to Simple where multiple values can be specified.
But unlike Simple routing, a health check is performed on every endpoint.
Unhealthy endpoint will not be returned.
IP-based routing
Create a list of CIDR blocks associated with a particular location.
The client will be directed to the location based on which CIDR blocks it falls into.
You cannot use an IP-based routing policy for records in a privately hosted zone.
Health Checks
Only for public resources
Types of Health Checks:
Health checks that monitor an endpoint
Monitors an endpoint that you specify either by IP address or by domain name
The endpoint must respond with an HTTP status code of 2xx or 3xx within two seconds after connecting
You can configure the health check to make requests similar to those of your users, such as requesting a web page from a specific URL.
You can search the response body for a string that you specify. The string must appear entirely in the first 5,120 bytes of the response body.
Health checks that monitor other health checks (calculated health checks)
The health check that does the monitoring is the parent health check, and the health checks that are monitored are child health checks.
You specify the number of child health checks that must be healthy for the status of the parent health check to be considered healthy
Health checks that monitor CloudWatch alarms
Monitor the data stream for the corresponding alarm instead of monitoring the alarm state.
If the data stream indicates that the state of the alarm is OK, the health check is considered healthy.
If the data stream indicates that the state is Alarm, the health check is considered unhealthy.
