How does Route 53 know when one AWS resource record is down using Failover policy?
Health Check is the way to inform Route 53 about a resource record. Failover records are created which makes use of health check. Suppose there are two resource records. There's one record for web1-east and another for web2-east, each pointing to the respective elastic IP address. Consider, web1-east. example. the host always resolves to the IP address 52. 206. 88. 55, no exceptions. Both records have the same name, www, the top record is the primary and points to web1-east and the second record is secondary and points to web2-east. Now when a client tries to reach www. example. host, Route 53 will return the IP address of web1-east because that's the resource listed in the primary failover record. Now let's say that web1-east crashes, someone shuts it down or the web application crashes or something like that. When another client comes along and tries to browse to www. example. host, Route 53 will return the secondary failover record pointing to web2-east. This concept follows an active/passive scenario. The record pointing to web1-east is always the primary or active record, unless that instance fails, in which case the secondary, or passive record, pointing to web2-east then takes over.