SAP-C02 Continuous Improvement for Existing Solutions Practice Question
A company uses AWS CloudFormation to manage infrastructure. The stack fails to update with the error: 'Resource handler returned message: The subnet 'subnet-xxx' is in use by a network interface.' The subnet is associated with a Lambda function in a VPC. The CloudFormation template is trying to delete the subnet. What should the company do to resolve this?
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
✓
Update the Lambda function configuration to remove the VPC settings, then delete the subnet.
To delete a subnet that is in use by a Lambda function's ENI, you must first disassociate the ENI. This can be done by updating the Lambda function configuration to remove the VPC settings, which causes Lambda to delete the ENI. After the ENI is deleted, you can delete the subnet. Option B is incorrect because the DeletionPolicy attribute only handles deletion, not update failures, and the subnet is still in use. Option C is incorrect because there is no force delete option for subnets; dependencies must be resolved first. Option D is incorrect because ENIs managed by Lambda cannot be manually deleted; you must update or delete the Lambda function.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Update the Lambda function configuration to remove the VPC settings, then delete the subnet.
Why this is correct
This releases the ENI, allowing subnet deletion.
- ✗
Modify the CloudFormation template to ignore the deletion failure using a DeletionPolicy attribute.
Why it's wrong here
DeletionPolicy can retain resources but does not resolve the dependency.
- ✗
Use the AWS CLI to force delete the subnet.
Why it's wrong here
Subnet cannot be force deleted if in use.
- ✗
Manually delete the Elastic Network Interface (ENI) from the AWS Management Console.
Why it's wrong here
ENI is managed by Lambda and cannot be manually deleted while in use.
Visual reference
Quick reference
Cloud Service Model Comparison
| Model | You Manage | Provider Manages | Examples |
|---|---|---|---|
| IaaS | OS, runtime, apps, data | Hardware, hypervisor, networking | EC2, Azure VMs, GCP Compute Engine |
| PaaS | Apps and data | OS, runtime, middleware, hardware | Elastic Beanstalk, Azure App Service |
| SaaS | Data and settings only | Everything else | Microsoft 365, Salesforce, Workday |
| FaaS / Serverless | Function code only | Infra, scaling, runtime | Lambda, Azure Functions, Cloud Run |
| CaaS | Containers and apps | Kubernetes, OS, hardware | EKS, AKS, GKE |
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This SAP-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 SAP-C02 exam.