DVA-C02 Troubleshooting and Optimization Practice Test 4 — 15 Questions

Question 1

A developer is deploying a CloudFormation stack and sees the event above. What should the developer do to fix the error?

Accepted Answer

Change the runtime to a supported version like nodejs18.x.. The error indicates that the runtime (Node.js 12.x) used in the Lambda function is deprecated and no longer supported by AWS. To fix this, the developer must update the CloudFormation template to specify a supported runtime version, such as nodejs18.x, and redeploy the stack. Option C correctly identifies this solution. Option A is incorrect because the programming language itself is not the issue; the runtime version needs updating. Option B is incorrect because increasing the timeout does not address the unsupported runtime. Option D is incorrect because adding permissions does not resolve the runtime deprecation error.

Answer

Update the Lambda function code to use a different programming language.

Answer

Increase the Lambda function timeout in the template.

Answer

Add permissions to the Lambda function's execution role.

Question 2

An application uses an Application Load Balancer (ALB) with a target group of EC2 instances. Users report intermittent HTTP 503 errors. The ALB access logs show that the error occurs when the request rate exceeds 10,000 requests per second. What is the most likely cause?

Accepted Answer

The ALB is exceeding its connection limit.. Application Load Balancers have a default limit of 10,000 new connections per second (this can be increased via a limit increase request). When the request rate exceeds this limit, the ALB returns HTTP 503 errors. Option A is incorrect because if EC2 instances were failing health checks, the ALB would route traffic to healthy instances, and the error would not be tied to a specific request rate. Option B is incorrect because an expiring SSL certificate would cause certificate validation errors, not 503 errors. Option D is incorrect because connection draining affects the graceful shutdown of instances and would not cause 503 errors when the request rate exceeds the ALB's limits.

Answer

The EC2 instances are failing health checks.

Answer

The SSL certificate is expiring.

Answer

The target group's connection draining is too short.

Question 3

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.. Network ACLs are stateless and block traffic unless explicitly allowed. The security group allows all outbound traffic, but if the network ACL's outbound rules are too restrictive, traffic can be blocked. Option A is wrong because the subnet has a route to an internet gateway. Option B is wrong because the security group allows all outbound traffic. Option D is wrong because the instance has a public IP address.

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 4

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.. 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 5

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.. With on-demand capacity, DynamoDB automatically scales to handle traffic, but hot partitions can still cause latency if a disproportionate amount of write traffic goes to a single partition. Even though overall consumed write capacity is below the provisioned limit (which is essentially unlimited for on-demand), and no throttling occurs, a hot partition can lead to contention and increased latency. Option A is incorrect because throttled events are zero. Option B is incorrect because read capacity units are irrelevant to write latency. Option C is incorrect because on-demand capacity does not have provisioned capacity; the table scales automatically, so insufficient provisioned capacity is not applicable. Option D correctly identifies hot partitions as the cause.

Answer

The table is experiencing write throttling.

Answer

The table has too many read capacity units.

Answer

The provisioned capacity is insufficient.

Question 6

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.. The 'Resource creation cancelled' error in AWS SAM indicates that the CloudFormation stack creation was cancelled because one or more resources failed to create, triggering a rollback. Option A is incorrect because a malformed SAM template would produce a validation error, not 'Resource creation cancelled'. Option C is incorrect because a Lambda function timeout is a runtime issue, not a deployment error. Option D is incorrect because insufficient IAM permissions would result in an access denied error, not this specific cancellation message.

Answer

The SAM template is malformed.

Answer

The Lambda function code has a timeout.

Answer

The IAM role does not have sufficient permissions.

Question 7

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.. 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 8

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.. S3 bucket names must be globally unique across all AWS accounts. If the specified bucket name already exists, the CloudFormation stack will fail to create the bucket. Option B is incorrect because S3 buckets do not require a VPC configuration. Option C is incorrect because a malformed bucket policy would cause a different error, and the error message specifically points to the bucket resource creation failure. Option D is incorrect because invalid Lambda function code would cause the Lambda resource to fail, not the S3 bucket.

Answer

The stack's VPC configuration is incorrect.

Answer

The S3 bucket policy is malformed.

Answer

The Lambda function code is invalid.

Question 9

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.. EC2 status checks monitor the health of your instances. There are two types: system status checks (which monitor the AWS systems on which your instance runs) and instance status checks (which monitor the software and network configuration of your individual instance). Security group rules do not affect these status checks. If a status check fails and the instance is unreachable via SSH, it is most likely due to an issue with the underlying host (system status check failure) or an OS-level issue. Therefore, a problem with the underlying host (Option C) is the most likely cause of a system status check failure.

Answer

The security group inbound rules are incorrect.

Answer

The instance has been terminated.

Answer

The key pair is missing.

Question 10

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.. To resolve an S3 bucket policy access issue, the developer should check both the bucket policy and the IAM user's attached policies. The bucket policy may contain an explicit deny that overrides allows, and the IAM user policy must also permit the action if the bucket policy does not. Option C and D are correct. Option A (S3 Transfer Acceleration) affects data transfer speed, not permissions. Option B (ACLs) can affect access but are a separate mechanism; they do not override an explicit deny in a bucket policy, and checking the bucket policy is the more direct step for this issue. Option E (CloudTrail) logs API calls but does not grant access.

Answer

Enable S3 Transfer Acceleration.

Answer

Verify the bucket's ACLs allow access.

Answer

Enable CloudTrail to log bucket access.

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.. 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.. 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

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. The most cost-effective way to troubleshoot this issue is to increase the function memory allocation to 2048 MB. In AWS Lambda, memory is proportional to CPU, so increasing memory speeds up processing, potentially reducing runtime below the 30-second timeout. This is more cost-effective than increasing the timeout (which doesn't fix the performance issue) or switching to EC2 (which is more expensive and not serverless). Dedicated instances are not available for Lambda.

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 14

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. Amazon RDS Performance Insights provides a quick visualization of database load and wait events, allowing the developer to identify the specific bottleneck without making changes. Option B is wrong because upgrading the instance class may help with resource constraints, but it is a reactive step taken after diagnosing the issue, not the first step. Option C is wrong because a read replica only offloads read traffic from the primary instance; it does not improve the performance of the slow query itself. Option D is wrong because the MySQL query cache is deprecated and not recommended for use in RDS for MySQL; even if enabled, it may not address the underlying performance degradation.

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

Question 15

A company runs a critical application on EC2 instances behind an Application Load Balancer. The application experiences intermittent 503 errors. The health checks are configured correctly and the instances pass health checks consistently. What is the most likely cause?

Accepted Answer

The application response time exceeds the ALB idle timeout. If the application response time exceeds the ALB idle timeout (default 60 seconds), the ALB returns a 503 error. This can happen intermittently if the application occasionally has slow responses. Option B is incorrect because if the health check path were wrong, instances would fail health checks consistently. Option C is incorrect because premature deregistration would cause instances to become unhealthy. Option D is incorrect because a security group blocking traffic would cause connection timeouts, not 503 errors.

Answer

The health check path is incorrect

Answer

The target group is deregistering instances prematurely

Answer

A security group is blocking traffic from the ALB to the instances