The answer is that the deployment group lacks a configured ECS service to deploy to. This error occurs because CodeDeploy requires a specific target resource—in this case, an Amazon ECS service—to orchestrate the Blue/Green deployment; without it, the deployment group has no instances or tasks to replace, causing the failure. On the AWS Certified Developer Associate DVA-C02 exam, this scenario tests your understanding that CodeDeploy deployment groups for ECS must explicitly reference an ECS service, not just a cluster or task definition. A common trap is assuming the error refers to EC2 instances or missing capacity, but for ECS Blue/Green deployments, “instances” means the ECS service itself. Remember: no service, no target—CodeDeploy can’t deploy to thin air.
DVA-C02 Deployment Practice Question
This DVA-C02 practice question tests your understanding of deployment. 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 development team uses AWS CodeDeploy to deploy a serverless application. The deployment fails with the error: 'The deployment failed because the deployment group did not contain any instances.' The deployment group is configured with an Amazon ECS service and uses the Blue/Green deployment type. 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
✓
The deployment group does not have a configured ECS service to deploy to.
The error 'The deployment failed because the deployment group did not contain any instances' indicates that CodeDeploy cannot find a target resource to deploy to. Since the deployment group is configured for an Amazon ECS service with Blue/Green deployment, the most likely cause is that the deployment group does not have an ECS service specified. Without a configured ECS service, CodeDeploy has no target to route traffic to or replace during the deployment, resulting in this error.
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 AppSpec file is incorrectly formatted and does not specify the task definition.
Why it's wrong here
Incorrect AppSpec causes validation errors, not 'no instances'.
✗
The deployment group's traffic routing configuration is set to 'AllAtOnce' causing immediate failure.
The CodeDeploy service role does not have permissions to describe ECS clusters.
Why it's wrong here
This would cause an access denied error, not 'no instances'.
✓
The deployment group does not have a configured ECS service to deploy to.
Why this is correct
CodeDeploy requires an ECS service to be specified in the deployment group; missing this results in no target instances.
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.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may confuse the 'no instances' error with missing EC2 instances, but in ECS deployments, 'instances' refers to the ECS service itself as the deployment target, not individual container instances.
Detailed technical explanation
How to think about this question
In CodeDeploy ECS Blue/Green deployments, the deployment group must reference an existing ECS service (via the ECS service name or Amazon Resource Name). CodeDeploy uses this service to identify the original task set and create a replacement task set. If the ECS service is not configured in the deployment group, CodeDeploy cannot resolve the target cluster or service, leading to the 'no instances' error because it treats the ECS service as the deployment target (analogous to EC2 instances in a traditional deployment).
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 company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
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.
Deployment — This question tests Deployment — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The deployment group does not have a configured ECS service to deploy to. — The error 'The deployment failed because the deployment group did not contain any instances' indicates that CodeDeploy cannot find a target resource to deploy to. Since the deployment group is configured for an Amazon ECS service with Blue/Green deployment, the most likely cause is that the deployment group does not have an ECS service specified. Without a configured ECS service, CodeDeploy has no target to route traffic to or replace during the deployment, resulting in this error.
What should I do if I get this DVA-C02 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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