Question 764 of 247
CodeDeploy Rolling Update Configuration — OneAtATime Deployment
A SysOps administrator needs to deploy an application to a set of EC2 instances in an Auto Scaling group. The deployment must be performed in batches, with each batch health-checked before proceeding. Which AWS CodeDeploy deployment configuration should be used?
Quick Answer
The answer is CodeDeployDefault.OneAtATime, because this predefined deployment configuration deploys the application to a single EC2 instance at a time within the Auto Scaling group, pausing to perform health checks on that batch before proceeding to the next. This ensures that if a deployment fails, only one instance is impacted, aligning perfectly with the requirement for batched, health-checked rollouts. On the AWS Certified SysOps Administrator Associate SOA-C02 exam, this question tests your understanding of CodeDeploy’s built-in configurations and their behavior with Auto Scaling groups—a common scenario where you must choose between AllAtOnce, HalfAtATime, and OneAtATime. The trap is selecting HalfAtATime, which deploys to 50% of instances simultaneously, or AllAtOnce, which risks full downtime. Remember the memory tip: “OneAtATime is the cautious climb—one step, check your footing, then the next.”
⚠ Common exam trap
Test-takers frequently confuse 'HalfAtATime' with a batch-based approach, but it does not health-check each individual instance before proceeding to the next batch; it only checks the overall health of the fleet after each batch, which can mask failures in specific instances.
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
✓
CodeDeployDefault.OneAtATime
CodeDeployDefault.OneAtATime is the correct deployment configuration because it deploys the application revision to one EC2 instance at a time, waiting for the instance to pass health checks before proceeding to the next. This ensures that the deployment is performed in batches of one, with each batch health-checked before moving on, which aligns with the requirement for batch-based, health-checked deployments.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
CodeDeployDefault.OneAtATime
Why this is correct
OneAtATime deploys to one instance at a time, with health checks between each.
- ✗
CodeDeployDefault.AllAtOnce
Why it's wrong here
AllAtOnce deploys to all instances at once, not in batches.
- ✗
CodeDeployDefault.HalfAtATime
Why it's wrong here
HalfAtATime deploys to half the instances at a time, not one by one.
- ✗
CodeDeployDefault.Custom
Why it's wrong here
Custom requires user-defined configuration, but the scenario fits the predefined OneAtATime.
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Same concept, more angles
1 more way this is tested on SOA-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 SysOps administrator needs to deploy a new application version to an Auto Scaling group without causing any downtime. The application runs on EC2 instances behind an Application Load Balancer. Which deployment method should the administrator use?
easy- A.Perform an in-place update by updating the launch template and manually replacing instances one by one.
- B.Use a rolling update with a batch size of 100% of the instances.
- ✓ C.Use a rolling update with a batch size of 1 instance and enable the health check grace period.
- D.Create a new Auto Scaling group with the new launch template and gradually shift traffic using a load balancer target group.
Why C: A rolling update with a batch size of 1 instance replaces instances one at a time, ensuring that the Auto Scaling group always maintains the desired capacity minus one, which prevents downtime. Enabling the health check grace period allows the new instance to pass the ALB health checks before the next instance is terminated, ensuring traffic is only sent to healthy instances.
Last reviewed: Jul 4, 2026
This SOA-C02 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the SOA-C02 exam.
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