PAS-C01 Blue/Green Deployment Practice Question
An organization runs SAP ERP on a single EC2 instance with a separate RDS for Oracle database. The Operations team needs to patch the operating system of the EC2 instance without causing downtime for the SAP application. What is the most effective approach?
⚠ Common exam trap
Candidates may think that creating an AMI and launching a new instance requires stopping the original instance, but you can create an AMI without stopping the instance.
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
✓
Create an AMI of the instance, launch a new instance from the AMI, and patch it.
It allows creating a patched copy of the instance without affecting the running SAP application. By creating an AMI of the running EC2 instance, you capture the current state. Launching a new instance from this AMI and patching it does not impact the original instance. Then you can redirect traffic to the new instance (e.g., by updating an Elastic IP or DNS) to complete the cutover with minimal downtime. This is a classic blue/green deployment pattern. Option B is incorrect because a rolling update requires multiple instances in an Auto Scaling group to maintain availability. With a single instance, there is no instance to serve traffic during the update. Option C is incorrect because AWS Systems Manager Patch Manager applies patches in-place, which typically requires a reboot, causing downtime for the SAP application. Option D is incorrect because most operating system patches require a reboot to take effect; running a script without rebooting does not fully apply the patches, leaving the system vulnerable and potentially not in compliance.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Create an AMI of the instance, launch a new instance from the AMI, and patch it.
Why this is correct
Correct. Creating an AMI from the running instance does not cause downtime. Launching a new instance from that AMI and patching it creates a patched copy. Then switching traffic to the new instance (e.g., via Elastic IP reassignment) achieves patching with minimal or no downtime.
- ✗
Use an Auto Scaling group with a launch template that references a patched AMI, and perform a rolling update.
Why it's wrong here
Incorrect. A rolling update requires at least two healthy instances to maintain availability. With a single instance, the Auto Scaling group cannot update without taking the instance out of service, causing downtime.
- ✗
Apply patches using AWS Systems Manager Patch Manager during a maintenance window.
Why it's wrong here
Incorrect. AWS Systems Manager Patch Manager applies patches directly to the running instance, which usually requires a reboot. This causes downtime for the SAP application.
- ✗
Use AWS Systems Manager to run a script that patches the OS without rebooting.
Why it's wrong here
Incorrect. Most OS patches require a reboot to apply fully. Running a script without rebooting does not complete the patching process, leaving the system vulnerable.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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