A company publishes an application at www.example.com through Route 53 failover routing, with a health check attached to the primary endpoint. The check starts reporting failures. Where do new DNS resolutions for the site go?
Show answer and explanation
Answer: A
Failover routing pairs a primary record with a standby record and binds the primary to a Route 53 health check. As long as the check passes, answers reference the primary; once it is marked unhealthy, Route 53 substitutes the standby record in its responses.
The switch happens purely at the DNS layer, so resolvers and clients start reaching the healthy endpoint on their next lookup without any client-side change.
Why the other options are wrong
- B. Route 53 does not black-hole traffic when a target fails; it returns the standby record so clients still receive a usable answer.
- C. DNS answers contain addresses, not application error codes, so a failing primary results in the secondary address being returned instead.
- D. DNS is a request-and-response protocol with no queueing; the resolver gets an immediate answer pointing at the healthy target.
Exam tip. Failover routing is only as good as the health check attached to the primary record.