The same service runs behind an ALB in each of two Regions. A Route 53 public hosted zone manages one IPv4 name. Return only the primary normally, and the secondary when the primary is unhealthy and the secondary is healthy.
ALB target-group health checks are configured, and their status is the DNS decision criterion. Secondary data and capacity are ready. No separate HTTP endpoint monitoring is required, and existing connections need not move immediately.
Choose TWO settings that meet the requirements.
Combine Primary and Secondary failover aliases with Evaluate Target Health to choose DNS answers from ALB target health.
Detailed explanation
Weighted distribution can return the secondary normally and does not express the required primary-only preference.
Weighted distribution can return the secondary normally and does not express the required primary-only preference.
TTL controls caching rather than target-health detection. Shortening it does not identify and exclude an unhealthy destination.
TTL controls caching rather than target-health detection. Shortening it does not identify and exclude an unhealthy destination.
Latency selection differs from a fixed Primary and Secondary relationship; a faster secondary can be chosen normally.
Latency selection differs from a fixed Primary and Secondary relationship; a faster secondary can be chosen normally.
The aliases reference the ALBs and express their priority in DNS responses.
The aliases reference the ALBs and express their priority in DNS responses.
This inherits the associated ALB target-group health for DNS selection. The stated criterion needs no additional Route 53 HTTP health check.
This inherits the associated ALB target-group health for DNS selection. The stated criterion needs no additional Route 53 HTTP health check.
Check official documentation
Compare the following points with the official documentation.
Review failover alias settings and ALB Evaluate Target Health conditions in the linked documentation.
Official references
- Official documentation 1
- Official documentation 2
- Official documentation 3
- Official documentation 4
- Official documentation 5
What to confirm
Explain primary-healthy, single-failure, and both-unhealthy answers, and the limits of DNS caching.
Key points
- Failover routing
- Evaluate Target Health
- ALB
- Weighted routing
- Latency routing
- DNS caching
Notes
- Environment: AWS SOA-C03 exam guide and the linked AWS documentation
- Reviewed against the linked AWS documentation on 2026-10-07.
Foundation review
Preference and health are separate settings
Create same-name, same-type Primary and Secondary aliases pointing to their ALBs. Evaluate Target Health inherits associated target-group health. Each associated group needs a healthy target; an empty group or one containing only unhealthy targets is unhealthy. An additional Route 53 health check, if associated, must pass as well as inherited health.
A DNS change does not complete recovery
A healthy primary is returned; an unhealthy primary with a healthy secondary returns the secondary. If both are unhealthy, the primary is returned, so failed destinations are not guaranteed to disappear from every answer. Resolver and client caches and existing connections do not move instantly. Prepare secondary data, capacity, dependencies, and recovery tests.