- A
Use CloudFormation stack update with 'UpdatePolicy' set to 'AutoScalingRollingUpdate' and 'MinInstancesInService' set to 0.
Why wrong: MinInstancesInService=0 allows all instances to be replaced at once, causing downtime.
- B
Delete the stack and recreate it with the new AMI.
Why wrong: Causes downtime.
- C
Use a CloudFormation update with a rolling update policy on the Auto Scaling group.
Rolling updates replace instances gradually.
- D
Create a custom resource backed by a Lambda function that updates the instance using AWS Systems Manager.
Custom resource can update the AMI without replacing the instance.
- E
Deploy the instances across multiple Availability Zones and update each zone separately.
Why wrong: This is a pattern for RDS, not for EC2 instances.
Question 1,423 of 1,750
Zero-Downtime AMI Updates with CloudFormation Rolling Update and Custom Resources
This DOP-C02 practice question tests your understanding of configuration management and iac. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 CloudFormation to manage infrastructure. They have a stack that includes a VPC, subnets, and EC2 instances. They want to update the AMI ID of an EC2 instance without causing downtime. Which TWO approaches meet this requirement?
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
✓
Use a CloudFormation update with a rolling update policy on the Auto Scaling group.
Option C is correct because CloudFormation's Auto Scaling group rolling update policy allows you to update the launch configuration or template (which includes the AMI ID) in a controlled, rolling fashion. By setting 'MinInstancesInService' to a value greater than 0, you ensure that a minimum number of instances remain in service during the update, preventing downtime. This approach replaces instances incrementally, so the application continues to serve traffic throughout the process.
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.
- ✗
Use CloudFormation stack update with 'UpdatePolicy' set to 'AutoScalingRollingUpdate' and 'MinInstancesInService' set to 0.
Why it's wrong here
MinInstancesInService=0 allows all instances to be replaced at once, causing downtime.
- ✗
Delete the stack and recreate it with the new AMI.
Why it's wrong here
Causes downtime.
- ✓
Use a CloudFormation update with a rolling update policy on the Auto Scaling group.
Why this is correct
Rolling updates replace instances gradually.
Related concept
Read the scenario before looking for a memorised answer.
- ✓
Create a custom resource backed by a Lambda function that updates the instance using AWS Systems Manager.
Why this is correct
Custom resource can update the AMI without replacing the instance.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Deploy the instances across multiple Availability Zones and update each zone separately.
Why it's wrong here
This is a pattern for RDS, not for EC2 instances.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse the 'AutoScalingRollingUpdate' policy with a generic EC2 instance update, not realizing it only applies to Auto Scaling groups, and they may incorrectly assume that setting 'MinInstancesInService' to 0 is acceptable for zero-downtime updates.
Detailed technical explanation
How to think about this question
Under the hood, CloudFormation's 'AutoScalingRollingUpdate' policy works by temporarily suspending the Auto Scaling group's health checks, then detaching and terminating old instances while attaching new ones from the updated launch template. The 'MinInstancesInService' parameter controls the minimum number of instances that must remain healthy during the update; setting it to 1 (or higher) ensures zero downtime. In real-world scenarios, you might combine this with a 'PauseTime' to allow application health checks to stabilize before proceeding to the next batch.
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
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
Visual reference
What to study next
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FAQ
Questions learners often ask
What does this DOP-C02 question test?
Configuration Management and IaC — This question tests Configuration Management and IaC — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use a CloudFormation update with a rolling update policy on the Auto Scaling group. — Option C is correct because CloudFormation's Auto Scaling group rolling update policy allows you to update the launch configuration or template (which includes the AMI ID) in a controlled, rolling fashion. By setting 'MinInstancesInService' to a value greater than 0, you ensure that a minimum number of instances remain in service during the update, preventing downtime. This approach replaces instances incrementally, so the application continues to serve traffic throughout the process.
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.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Same concept, more angles
1 more ways this is tested on DOP-C02
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A company uses AWS CloudFormation to manage infrastructure. They have a production stack that creates an Auto Scaling group. They want to update the launch configuration to use a new Amazon Machine Image (AMI) ID without causing downtime. Which update policy should they set on the Auto Scaling group?
medium- A.AutoScalingScheduledAction
- B.AutoScalingReplacingUpdate
- ✓ C.AutoScalingRollingUpdate
- D.AutoScalingBatchUpdate
Why C: Option C is correct because the AutoScalingRollingUpdate policy allows CloudFormation to update the Auto Scaling group's launch configuration by gradually replacing instances in batches, ensuring that a minimum number of instances remain in service throughout the update. This prevents downtime by terminating old instances and launching new ones with the updated AMI in a controlled, rolling fashion.
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Last reviewed: Jul 4, 2026
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