DOP-C02 Resilient Cloud Solutions Practice Question
A company runs a Stateful application on EC2 that requires sticky sessions. They use an ALB with duration-based stickiness. During a deployment, they want to drain existing connections gracefully before terminating instances. Which step is necessary?
⚠ Common exam trap
Candidates often confuse 'connection draining' (which is the deregistration delay on ALB target groups) with 'sticky session duration' or 'health check settings,' thinking that reducing stickiness or marking instances unhealthy alone will gracefully terminate connections, when in fact the deregistration delay is the specific mechanism that waits for in-flight requests to complete.
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 target group.
ALB target groups use a 'deregistration delay' (formerly called connection draining) to allow in-flight requests to complete before an instance is terminated. This setting is configured on the target group, not the load balancer, and it works with sticky sessions by waiting for the delay period (default 300 seconds) for existing connections to finish, even if the stickiness cookie would otherwise route new requests to the same instance. During a deployment, increasing this delay or ensuring it is set appropriately is the necessary step to gracefully drain connections.
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 deregistration delay on the target group.
Why it's wrong here
Increasing the deregistration delay is not necessarily required; the necessary step is to enable connection draining (i.e., set a non-zero deregistration delay). While increasing the delay could help, it is not the core requirement. Enabling the feature is what allows in-flight requests to complete.
- ✗
Reduce the stickiness duration to zero.
Why it's wrong here
Reducing the stickiness duration to zero does not help drain existing connections. It only stops new sessions from being sticky, but existing sticky sessions will continue to route to the same instance until the cookie expires. The instance can still be terminated without waiting for those requests.
- ✗
Configure health checks to mark instances unhealthy.
Why it's wrong here
Configuring health checks to mark instances unhealthy stops new traffic but does not wait for in-flight requests to finish. Without connection draining, the instance can be deregistered immediately and terminated while requests are still being processed.
- ✓
Enable connection draining on the target group.
Why this is correct
Enabling connection draining (deregistration delay) on the target group is the necessary step. It configures the ALB to wait for in-flight requests to complete before fully deregistering the instance, allowing graceful termination even with sticky sessions.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This DOP-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 DOP-C02 exam.