CV0-004 Operations and Support Practice Question
A cloud administrator manages an Amazon EC2 Auto Scaling group behind an Application Load Balancer. Users report intermittent 502 errors during scale-in events. Logs show that instances are terminated while still serving in-flight requests. Which configuration change should the administrator make to resolve this?
⚠ Common exam trap
Watch out — candidates often confuse scale-in tuning knobs like cooldown or health check type with the actual graceful-drain mechanism that controls when an instance is removed from service.
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
✓
Enable connection draining on the load balancer and increase the deregistration delay to allow in-flight requests to complete before instance termination.
The 502 errors occur because instances are terminated while still processing requests. Enabling connection draining with an appropriate deregistration delay makes Auto Scaling wait until the load balancer confirms the target is no longer receiving traffic before terminating it, allowing in-flight requests to complete and eliminating the error condition.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Increase the Auto Scaling group's cooldown period so that scale-in events occur less frequently throughout the day.
Why it's wrong here
Cooldown only delays subsequent scaling activities after a scaling event; it does not change how an instance is removed. When scale-in eventually happens, the instance is still terminated without waiting for in-flight requests, so the 502 errors continue to occur at a lower frequency rather than being resolved.
- ✗
Enable sticky sessions on the load balancer so that each user's requests are consistently routed to the same backend instance.
Why it's wrong here
Sticky sessions improve session affinity but do not prevent instance termination during scale-in. When a sticky-bound instance is removed, the user's next request is routed to a different target and any in-flight request on the terminated instance still fails, so the 502 errors are not resolved by this change.
- ✓
Enable connection draining on the load balancer and increase the deregistration delay to allow in-flight requests to complete before instance termination.
Why this is correct
Connection draining, implemented as deregistration delay on the target group, keeps the target in a draining state while existing connections finish. Auto Scaling waits for the load balancer to report the target as unused before terminating the instance, which prevents in-flight requests from being cut off and eliminates the 502 errors observed during scale-in.
- ✗
Change the health check type from ELB to EC2 so that the Auto Scaling group relies on instance status checks instead of load balancer health.
Why it's wrong here
Switching to EC2 health checks makes the Auto Scaling group ignore load balancer health signals, which can cause unhealthy targets to remain in service. It also does not address the graceful removal of instances during scale-in, so in-flight requests are still terminated abruptly and 502 errors persist.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official CompTIA exam blueprint
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