- A
The CloudWatch alarm that triggered the rollback also stopped the old task set.
Why wrong: CloudWatch alarms do not stop tasks; they can trigger rollback but not stop old tasks.
- B
CodeDeploy did not drain connections from the Application Load Balancer before terminating the old task set.
Why wrong: Connection draining is not directly related to health of old tasks after rollback.
- C
The ECS service auto-scaling policy reduced the desired count of the old task set during the deployment.
Why wrong: Auto-scaling does not reduce count during blue/green deployment; CodeDeploy manages task sets.
- D
The new application version changed the database schema, which broke the old version after rollback.
Database schema changes are not automatically rolled back, causing incompatibility.
DOP-C02 SDLC Automation Practice Question
This DOP-C02 practice question tests your understanding of sdlc 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 runs a critical application on Amazon ECS with Fargate. They use blue/green deployments via AWS CodeDeploy. During a recent deployment, the new task set failed health checks and CodeDeploy automatically rolled back. However, the old task set also became unhealthy shortly after rollback. What could explain this?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
The new application version changed the database schema, which broke the old version after rollback.
Option D is correct because a backward-incompatible database schema change (e.g., a column removal or renaming) applied by the new application version can corrupt or invalidate the data that the old version relies on. When CodeDeploy rolls back to the old task set, the old application cannot function correctly with the altered schema, causing it to fail health checks. This is a classic rollback failure scenario where the deployment changes shared state (the database) that persists beyond the task set lifecycle.
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 CloudWatch alarm that triggered the rollback also stopped the old task set.
Why it's wrong here
CloudWatch alarms do not stop tasks; they can trigger rollback but not stop old tasks.
- ✗
CodeDeploy did not drain connections from the Application Load Balancer before terminating the old task set.
Why it's wrong here
Connection draining is not directly related to health of old tasks after rollback.
- ✗
The ECS service auto-scaling policy reduced the desired count of the old task set during the deployment.
Why it's wrong here
Auto-scaling does not reduce count during blue/green deployment; CodeDeploy manages task sets.
- ✓
The new application version changed the database schema, which broke the old version after rollback.
Why this is correct
Database schema changes are not automatically rolled back, causing incompatibility.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume rollback always restores full functionality, overlooking that shared mutable state (like a database schema) can persist across deployments and break the old version after rollback.
Detailed technical explanation
How to think about this question
Under the hood, CodeDeploy creates a replacement task set and shifts traffic using an ALB test listener and production listener. During rollback, it reweights the production listener to 100% for the original task set, but the original task set's containers still share the same database. If the new version applied a schema migration (e.g., ALTER TABLE ... DROP COLUMN), the old version's queries may fail with errors like 'column not found', causing health check endpoints to return 5xx. This is why immutable infrastructure patterns often recommend deploying database changes separately from application code, or using additive-only schema changes.
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.
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FAQ
Questions learners often ask
What does this DOP-C02 question test?
SDLC Automation — This question tests SDLC Automation — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The new application version changed the database schema, which broke the old version after rollback. — Option D is correct because a backward-incompatible database schema change (e.g., a column removal or renaming) applied by the new application version can corrupt or invalidate the data that the old version relies on. When CodeDeploy rolls back to the old task set, the old application cannot function correctly with the altered schema, causing it to fail health checks. This is a classic rollback failure scenario where the deployment changes shared state (the database) that persists beyond the task set lifecycle.
What should I do if I get this DOP-C02 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jul 4, 2026
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