Ref: https://learn.cantrill.io/courses/1820301/lectures/41301582

• Summary:
• Contents:

R53 Routing Policies 101

• 🔧 Set of rules defining how to respond to DNS queries sent to your R53-hosted domain
  • Clients receive IP addresses or AWS resources as response to their queries
• Rule conditions can be based on
  • Resource health
  • Geography
  • Testing phases
  • Load balancing
  • …
• Useful for
  • Optimizing traffic distribution
  • Improving latency
  • Configuring resilience and failover
  • …
• 💡 R53 has a range of routing policies that you can choose for your regional and global infrastructure. We will go into details of each routing policy and compare them

R53 Simple Routing - Architecture

Diagram: https://github.com/acantril/aws-sa-associate-saac03/blob/main/1200-ROUTE53/00_LEARNINGAIDS/Route53SimpleRouting-1.png

• 🔧 One record per host name. Each record can have multiple values.
  • e.g. For host www, we assign an A record with multiple values (IPv4 addresses)
  • When client requests to resolve www, all values are returned in a random order
  • Client chooses one of the values and connects to the server
• 👍 Simple → use it to route requests towards ONE single service (e.g. web server)
  • Simple Routing is the DEFAULT routing policy in R53
• ‼️ 👎 Limitation: does NOT support health checks!!
  • No way of knowing if pointed resource is operational or not
  • All other R53 routing policies support health checks & routing intelligence based on them
• 💡 Simple routing is quite limited & inflexible, but simple to implement & manage