Amazon Route 53

• It is a highly available, scalable, fully managed and authoritative DNS
  • Authoritative: the customer can update the DNS records
• Route 53 is also a Domain Registrar
• We have the ability to check the health of our resources to which we create DNS records
• It is the only AWS service which provides 100% availability SLA

DNS Records

• Each record contains:
  • Domain/subdomain name: example com
  • Record type: A, AAAA, CNAME, etc.
  • Value: for example an IP address
  • Routing Policy: how Route 53 responds to queries
  • TTL: amount of time the record is cached at the DNS server
• Route 53 supports a bunch of record types:
  • A / AAAA/ CNAME / NS
  • Advanced records: CAA / DS / MX / NAPTR / PTR / SOA / TXT / SPF / SRV
• Important record types (from the exam perspective):
  • A: maps a hostname to an IPv4 address
  • AAAA : maps a hostname to an IPv6 address
  • CNAME: maps a hostname to another hostname:
    • The target is a domain name which must have an A or AAAA record
    • We can’t create a CNAME record for the top node of a DNS namespace (Zone Apex)
  • NS: Name Servers for the Hosted Zone

Hosted Zones

• Hosted Zones are containers for records that define how to route traffic to a domain and its subdomains
• Public Hosted Zones: contains records that specify how to route traffic on the internet
• Private Hosted Zones: contains records that can be resolved within one or more VPCs (private domain names)
• We pay $0.5 per month for any hosted zone we create

Routing Policies

Weighted

• We control the % of the requests that go to each specific resource
• We assign each record with a relative weight:
  • Weights don’t need to sum up to 100%
• DNS records must have the same name and type
• They can be associated with health checks
• Use cases: load balancing between regions, testing new application versions, etc.
• We can assign a weight of 0 to a record to stop sending traffic to the resource
• If all the records have weight of 0, then all the resources will resolved equally

Latency-based

• The hosted zone will resolve the resource that has the least latency for the requestor
• Helpful when latency is a priority for the users
• Latency is based on traffic between users and AWS Regions
• Records can be associated with health checks

Failover (Active-Passive)

• With a Failover record, Route 53 actively returns a primary resource
• If there is a failure for the primary resource, the secondary resource will be returned
• When creating a Failover record, we have to select if the record is primary or secondary