The answer is a failed health check triggering a rollback during the rolling update. In a rolling update with a batch size of 1, Elastic Beanstalk updates one instance at a time, then checks its health. If that single new instance fails the health check, the deployment is automatically rolled back, and all instances are reverted to the old application version. This process of swapping instances—launching a new one, failing, then replacing it with the old version—causes intermittent 503 errors as the load balancer cycles through unhealthy endpoints. On the AWS Certified SysOps Administrator Associate SOA-C02 exam, this scenario tests your understanding of deployment policies and health check integration; a common trap is assuming a 503 always means a code bug, when it often points to a rollback mechanism. Remember the memory tip: “Batch of one, rollback undone”—if the first batch fails, the whole deployment reverts, leaving old code running.
SOA-C02 Deployment, Provisioning, and Automation Practice Question
This SOA-C02 practice question tests your understanding of deployment, provisioning, and automation. 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 uses AWS Elastic Beanstalk to deploy a web application. The environment is configured with a load balancer and an Auto Scaling group. Recently, the development team updated the application code and deployed it via Elastic Beanstalk. After the deployment, users report intermittent 503 errors. The SysOps administrator checks the environment health and sees that it is 'Severe' with many instances being replaced. The administrator notices that the new instances are being launched with the old application version. The deployment was a rolling update with a batch size of 1. What is the MOST likely cause of the issue?
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
✓
The deployment failed health checks on the first instance and rolled back, replacing all instances with the old version.
Option C is correct because in a rolling update with batch size 1, instances are updated one at a time. If the health check fails for the new batch, the deployment is rolled back, and the new instances are replaced with the old version. This would cause intermittent 503 errors as instances are being swapped. Option A is incorrect because the environment URL does not change. Option B is incorrect because the load balancer stickiness would not cause version mismatches. Option D is incorrect because the health check URL is not changed by deployment.
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.
✓
The deployment failed health checks on the first instance and rolled back, replacing all instances with the old version.
Why this is correct
Why C is correct
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 load balancer is configured with sticky sessions, causing requests to go to outdated instances.
Why it's wrong here
Why B is wrong
✗
The Elastic Beanstalk environment URL was changed during the deployment.
Why it's wrong here
Why A is wrong
✗
The health check URL was not updated to reflect the new application version.
Why it's wrong here
Why D is wrong
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→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 SOA-C02 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Deployment, Provisioning, and Automation — This question tests Deployment, Provisioning, and Automation — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The deployment failed health checks on the first instance and rolled back, replacing all instances with the old version. — Option C is correct because in a rolling update with batch size 1, instances are updated one at a time. If the health check fails for the new batch, the deployment is rolled back, and the new instances are replaced with the old version. This would cause intermittent 503 errors as instances are being swapped. Option A is incorrect because the environment URL does not change. Option B is incorrect because the load balancer stickiness would not cause version mismatches. Option D is incorrect because the health check URL is not changed by deployment.
What should I do if I get this SOA-C02 question wrong?
Identify which SOA-C02 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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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