This ANS-C01 practice question tests your understanding of network design. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A company is deploying a critical application across three AWS Regions using an active-active architecture with Amazon Route 53 latency-based routing. Each region has an Application Load Balancer (ALB) as the endpoint. The application health checks are configured to check the /health endpoint every 10 seconds. During a regional failure, some users experience timeouts while others are redirected correctly. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Route 53 health checkers take multiple intervals to detect failure, and timeouts occur before failover completes.
Route 53 health checkers operate from multiple global locations and evaluate the /health endpoint every 10 seconds. However, to declare an endpoint unhealthy, Route 53 requires a configurable number of consecutive failures (default is 3), meaning it can take 30 seconds or more before the DNS record is updated to remove the failed region. During this detection window, some users whose DNS queries are answered by Route 53 before the failure is fully propagated may receive the IP of the failing ALB, leading to timeouts, while others who query after the failover complete successfully.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Route 53 health checkers take multiple intervals to detect failure, and timeouts occur before failover completes.
Why this is correct
Route 53 health checks have a 30-second interval and multiple checks are needed to confirm failure.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The ALB health check is misconfigured and returns a non-200 status code during normal operation.
Why it's wrong here
The ALB health check is separate from Route 53 health check.
✗
The TTL on the Route 53 record is set too low, causing stale DNS responses.
Why it's wrong here
Low TTL reduces caching, not timeouts.
✗
Users have cached DNS records from the failed region, and Route 53 does not return healthy endpoints.
Why it's wrong here
DNS caching can cause delays but not timeouts if failover is working.
Common exam traps
Common exam trap: answer the scenario, not the keyword
AWS often tests the misconception that Route 53 instantly fails over when an endpoint becomes unhealthy, but the trap here is that health check detection requires multiple consecutive failures (default 3) before the endpoint is removed from DNS responses, causing a delay that leads to intermittent timeouts for some users.
Detailed technical explanation
How to think about this question
Route 53 health checkers use a distributed network of checkers that each independently evaluate the endpoint; the failure threshold (e.g., 3 out of 3 failures) must be met before the endpoint is marked unhealthy, and DNS TTLs (commonly 60 seconds) further delay propagation. In an active-active setup with latency-based routing, Route 53 selects the region with the lowest latency among healthy endpoints, but during the detection window, a failing region may still be considered healthy, causing some users to be routed to it. This behavior is governed by the Route 53 health check settings, including the request interval and failure threshold, which directly impact the time to failover.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Network Design — This question tests Network Design — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Route 53 health checkers take multiple intervals to detect failure, and timeouts occur before failover completes. — Route 53 health checkers operate from multiple global locations and evaluate the /health endpoint every 10 seconds. However, to declare an endpoint unhealthy, Route 53 requires a configurable number of consecutive failures (default is 3), meaning it can take 30 seconds or more before the DNS record is updated to remove the failed region. During this detection window, some users whose DNS queries are answered by Route 53 before the failure is fully propagated may receive the IP of the failing ALB, leading to timeouts, while others who query after the failover complete successfully.
What should I do if I get this ANS-C01 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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