DVA-C02 Troubleshooting and Optimization Practice Test 8 — 15 Questions

Question 1

A developer is troubleshooting an EC2 instance that cannot connect to the internet. The instance has a public IP address and is in a public subnet with a route to an internet gateway. The security group allows all outbound traffic. What is the most likely cause?

Accepted Answer

The network ACL's outbound rules are blocking traffic.. Option D is correct because a missing or misconfigured network ACL can block traffic even if security group allows it. Option A is wrong because the instance has a public IP. Option B is wrong because the route table has a route to an internet gateway. Option C is wrong because outbound is allowed.

Answer

The subnet's route table does not have a route to an internet gateway.

Answer

The security group's outbound rules are too restrictive.

Answer

The instance does not have a public IP address.

Question 2

A company's application running on Amazon ECS Fargate is experiencing high CPU utilization. The task definition has CPU set to 256 units. What should be done to improve performance?

Accepted Answer

Increase the CPU value in the task definition and redeploy the service.. Option B is correct because increasing CPU units in the task definition and redeploying the service will allocate more CPU to the tasks. Option A is wrong because horizontal scaling can help but the root cause is insufficient CPU per task. Option C is wrong because increasing memory does not affect CPU. Option D is wrong because changing the launch type changes billing but not CPU allocation.

Answer

Increase the desired count of tasks.

Answer

Increase the memory value in the task definition.

Answer

Switch to EC2 launch type.

Question 3

An application uses DynamoDB as its database with on-demand capacity. The application experiences increased latency during peak hours. CloudWatch metrics show ConsumedWriteCapacityUnits is below ProvisionedWriteCapacityUnits, but ThrottledWriteEvents is zero. What is the most likely cause?

Accepted Answer

The workload has hot partitions.. Option C is correct because even though capacity is not exceeded, hot partitions can cause latency. On-demand capacity is per-table, not per-partition. Option A is wrong because throttled events are zero. Option B is wrong because on-demand capacity is automatically managed. Option D is wrong because RCUs are not related to write latency.

Answer

The table is experiencing write throttling.

Answer

The table has too many read capacity units.

Answer

The provisioned capacity is insufficient.

Question 4

A developer is deploying a serverless application using AWS SAM. The deployment fails with the error 'Resource creation cancelled'. What is the most likely cause?

Accepted Answer

A resource in the stack failed to create.. Option D is correct because 'Resource creation cancelled' typically indicates a stack failure due to a previous resource creation failure. Option A is wrong because missing permissions cause access denied errors. Option B is wrong because timeout would cause a different error. Option C is wrong because invalid YAML causes a parse error.

Answer

The SAM template is malformed.

Answer

The Lambda function code has a timeout.

Answer

The IAM role does not have sufficient permissions.

Question 5

An application running on EC2 instances behind an Application Load Balancer is experiencing high error rates. The ALB target group health checks are failing. The instances are in an Auto Scaling group with a minimum of 2 and maximum of 10. What should a developer do to troubleshoot?

Accepted Answer

Check the EC2 instance system log and screenshot.. Option A is correct because checking the instance system log and screenshot helps diagnose OS-level issues. Option B is wrong because that only shows traffic. Option C is wrong because scaling policies don't affect health check failures. Option D is wrong because increasing max size doesn't fix existing instances.

Answer

Review the ALB access logs.

Answer

Modify the Auto Scaling group's scaling policy.

Answer

Increase the maximum size of the Auto Scaling group.

Question 6

A developer is using AWS CloudFormation to deploy a stack that includes an S3 bucket and a Lambda function. The stack fails with the error 'The following resource(s) failed to create: [MyBucket]'. What is the most likely cause?

Accepted Answer

The S3 bucket name is already taken.. Option C is correct because S3 bucket names must be globally unique. Option A is wrong because Lambda function errors would not cause bucket failure. Option B is wrong because CloudFormation does not require a VPC. Option D is wrong because S3 bucket policies are not required for creation.

Answer

The stack's VPC configuration is incorrect.

Answer

The S3 bucket policy is malformed.

Answer

The Lambda function code is invalid.

Question 7

A developer receives an alert that an EC2 instance's status check fails. The instance is running, but the developer cannot SSH into it. What is the most likely cause?

Accepted Answer

There is a problem with the underlying host.. A status check failure on a running EC2 instance indicates that the instance is passing the system status check (i.e., the underlying host is operational) but failing the instance status check, which tests network connectivity, OS responsiveness, and file system integrity. Since the instance is running but SSH is unavailable, the most likely cause is a problem with the underlying physical host (e.g., hardware degradation, network connectivity loss at the hypervisor level) that prevents the instance from responding to network traffic, even though the instance state shows as 'running'.

Answer

The security group inbound rules are incorrect.

Answer

The instance has been terminated.

Answer

The key pair is missing.

Question 8

A developer is troubleshooting an issue where an S3 bucket policy is not granting access to an IAM user. Which TWO actions should the developer take to resolve the issue?

Accepted Answer

Check the bucket policy for any explicit denies.. Option A and C are correct because checking the bucket policy and IAM user policy are the two places where permissions are evaluated. Option B is wrong because ACLs are legacy. Option D is wrong because CloudWatch does not show bucket policies. Option E is wrong because S3 Transfer Acceleration is not related to permissions.

Answer

Enable S3 Transfer Acceleration.

Answer

Verify the bucket's ACLs allow access.

Answer

Enable CloudTrail to log bucket access.

Question 9

A developer is using AWS X-Ray to trace a Lambda function that calls DynamoDB and SQS. Some traces show errors. Which THREE actions should the developer take to diagnose the issue?

Accepted Answer

Examine the trace details for exception messages.. Option A is correct because examining trace details in AWS X-Ray allows the developer to view exception messages, stack traces, and error codes for each segment of the trace. This directly reveals the root cause of errors, such as DynamoDB throttling or SQS permission issues, by pinpointing which service call failed and why.

Answer

Disable X-Ray sampling to capture all requests.

Answer

Enable CloudFront to cache responses.

Question 10

A developer is troubleshooting a slow RDS MySQL instance. Which TWO metrics in Amazon CloudWatch should the developer examine first?

Accepted Answer

CPUUtilization. Options A and E are correct because high CPU and high ReadLatency are common indicators of database performance issues. Option B is wrong because FreeStorageSpace is for storage capacity, not performance. Option C is wrong because NetworkReceiveThroughput is for network. Option D is wrong because SwapUsage is less common for RDS.

Answer

NetworkReceiveThroughput

Answer

SwapUsage

Answer

FreeStorageSpace

Question 11

Refer to the exhibit. A developer attached this S3 bucket policy to my-bucket. Users from IP 10.0.0.5 can access objects, but users from IP 10.0.1.5 cannot. What is the most likely reason?

Accepted Answer

The IP address condition restricts access to a specific range.. Option D is correct because the policy only allows access from the IP range 10.0.0.0/24. Users from 10.0.1.5 are outside this range. Option A is wrong because the resource is correct. Option B is wrong because the action is correct. Option C is wrong because the bucket policy allows access.

Answer

The bucket policy does not apply to users.

Answer

The action should be s3:GetObjectVersion.

Answer

The resource ARN is incorrect.

Question 12

Refer to the exhibit. A developer invoked a Lambda function and received this response. What does the FunctionError field indicate?

Accepted Answer

The function threw an unhandled exception.. Option B is correct because FunctionError: Unhandled indicates that the function threw an exception that was not caught by the code. Option A is wrong because StatusCode 200 means invocation succeeded. Option C is wrong because throttling would return 429. Option D is wrong because configuration errors would return 400.

Answer

The function executed successfully.

Answer

The function was throttled.

Answer

The function timed out.

Question 13

Refer to the exhibit. A developer created this CloudFormation template. After deployment, the stack creation fails with 'Bucket name already exists'. What should the developer do to fix the issue?

Accepted Answer

Change the BucketName to include a random suffix.. Option B is correct because the bucket name is derived from the stack name, which might be already used. Changing the bucket name to include a unique suffix will avoid conflicts. Option A is wrong because removing versioning does not affect bucket name uniqueness. Option C is wrong because the queue is not the issue. Option D is wrong because disabling SSE does not affect naming.

Answer

Remove the MyQueue resource.

Answer

Remove the VersioningConfiguration from the bucket.

Answer

Set SqsManagedSseEnabled to false.

Question 14

A Lambda function that processes S3 events is failing with timeout errors. The function downloads a 100 MB file from S3 and processes it. The current timeout is 30 seconds. What is the most cost-effective way to troubleshoot this issue?

Accepted Answer

Increase the function memory allocation to 2048 MB. Option B is correct because increasing the function's memory also increases CPU allocation, which can speed up processing and reduce runtime. Option A is wrong because Lambda supports up to 15 minutes, but increasing timeout without addressing performance may not help. Option C is wrong because using a larger instance type is not applicable to Lambda. Option D is wrong because Lambda does not support dedicated instances.

Answer

Use a larger EC2 instance type instead of Lambda

Answer

Increase the function timeout to 5 minutes

Answer

Provision a dedicated Lambda instance for the function

Question 15

A developer is troubleshooting a slow-running Amazon RDS for MySQL query. The query performance has degraded over time. Which approach should the developer take first to identify the cause?

Accepted Answer

Enable Performance Insights and review the database load. Option C is correct because enabling RDS Performance Insights gives a quick view of database load and wait events. Option A is wrong because query caching is not directly available in RDS MySQL and may not help. Option B is wrong because a read replica does not fix the performance issue. Option D is wrong because increasing instance size may be unnecessary without first diagnosing the bottleneck.

Answer

Upgrade the DB instance to a larger instance class

Answer

Create a read replica to offload read traffic

Answer

Enable the MySQL query cache