Route 53

• Route 53 is a managed DNS (Domain Name System)
• DNS is a collection of rules and records which helps clients to understand how to reach a server through its domain name
• In AWS, the most common records are:
  • A: hostname to IPv4
  • AAAA: hostname to IPv6
  • CNAME: hostname to hostname
  • Alias: hostname to AWS resource
• Route 53 can use:
  • Public domain we own
  • Private domain names that can be resolved in our VPCs
• Route 53 has advanced features such as:
  • Load balancing (through DNS - also called client load balancing)
  • Health checks
  • Route policy: simple, failover, geo-location, latency, weighted, multi value
• We pay $0.5 per moth per hosted zone

DNS Record TTL

• DNS Record TTL - Time to Live: used to not overload the DNS server with queries. We can set a TTL for a DNS, while the TTL is not passed, the client wont hit the DNS server
• High TTL (example: 24h):
  • Less traffic on the DNS server
  • Possibility to have outdated records
• Low TTL (example: 60s):
  • More traffic on the DNS server
  • Records are outdated for more often
  • Easy to change records
• It is mandatory for each DNS record the specify a TTL

CNAME vs Alias

• AWS resources (LB, CloudFront) expose a AWS hostname
• CNAME:
  • Points a hostname to any other hostname
  • It only works for non root domains!
• Alias:
  • Points a hostname to an AWS resource
  • Work for both root and non-root domains
  • They are free of charge
  • Have native health check capabilities

Health Checks

• An IP is healthy if it fails X (default 3) health checks in a row
• After X health checks passed it can become available again
• Default health checks interval is 30 seconds, with possibility of fast health checks (up to 10s)
• About 15 health checkers will check the endpoint health => one request every 2 seconds on average
• We can have HTTP, TCP and HTTPS health checks (no SSL verification)
• Health checks can be integrated with CloudWatch
• Health checks can be linked to Route 53 DNS queries

Simple Routing Policy

• We can use it when we need to redirect to a single resource
• We can’t attach health checks to simple routing policies
• If multiple values are return, a radom IP is chosen by the client

Weighted Routing Policy

• Controls the percentage of the requests which go to specific end-points
• Helpful to test a given percentage of traffic on new application version
• Helpful to split traffic between regions
• Can be associated with multiple health checks

Latency Routing Policy

• Redirects to the server that has the least latency close to the user
• Latency is evaluated in terms of user to designated AWS region

Failover Routing Policy

• Requires a primary record and a secondary record (disaster recovery)
• If the primary record fails, traffic is routed to the secondary record
• Requires a health check in order to work, failover is detected based on health checks

Geo-location Routing Policy

• It is routing based on the user’s location
• We can specify where the traffic should be routed if the user is requesting from an IP that originates from a country
• Requires a default policy (in case there is no match for a location)

Geo-proximity Routing Policy

• It is also routing based on the user’s location
• We can optionally choose to route more traffic or less to a given resource by specifying a value known as bias
• To use geo-proximity routing, we must use Route 53 traffic flow
• We create geo-proximity rules for our resources and specify one of the following values for each rule:
  • If we are using AWS resources, the AWS Region that you created the resource in
  • If we are using non-AWS resources, the latitude and longitude of the resource

Multi Value Routing Policy

• Can be used when we need to route traffic to multiple resources and we want to associate Route53 health checks to the records
• It will return up to 8 healthy records for each Multi Value query
• It is not a substitute for Elastic Load Balancer!

Route 53 as a Registrar

• A domain name registrar is an organization that manages the reservation of internet domain names. Some domain registrars are: GoDaddy, Google Domain and also Route 53
• It is possible to use a third party domain registrar with AWS. In order to use a domain bought from the third party, we have to do the following:
  1. Create a hosted zone in Route53
  2. Update NS records on 3rd party website to use Route 53 name servers