DVA-C02 Troubleshooting and Optimization Practice Test 16 — 15 Questions

Question 1

A developer is troubleshooting an AWS CloudFormation stack creation failure. The stack creation failed with the error: 'Resource creation cancelled'. What does this error typically indicate?

Accepted Answer

Another resource in the stack failed, causing a rollback.. Option B is correct because 'Resource creation cancelled' means a different resource in the stack failed, causing rollback. Option A is wrong because insufficient IAM permissions would give an access denied error. Option C is wrong because the error is not about template validation. Option D is wrong because the error is not about resource limit.

Answer

The IAM user does not have permission to create the resource.

Answer

The template has a syntax error.

Answer

The resource type is not supported by CloudFormation.

Question 2

A developer is using AWS Elastic Beanstalk to deploy a web application. The application is experiencing high latency. Which TWO steps should the developer take to troubleshoot and optimize the application?

Accepted Answer

Enable AWS X-Ray integration and analyze service maps.. Option B is correct because enabling enhanced health reporting provides detailed metrics. Option D is correct because enabling X-Ray integration provides tracing to identify bottlenecks. Option A is wrong because deploying to a different region might not help latency for existing users. Option C is wrong because increasing instance size could help but not a troubleshooting step. Option E is wrong because RDS is not involved.

Answer

Configure an Amazon RDS read replica.

Answer

Increase the instance type to a larger size.

Answer

Deploy the application to a different AWS region.

Question 3

A developer is optimizing an AWS Lambda function that processes streaming data from Amazon Kinesis. The function is CPU-bound. Which TWO actions should the developer take to improve performance?

Accepted Answer

Rewrite the function in a compiled language like Go.. Option A is correct because increasing memory also increases CPU allocation. Option C is correct because using a language with better CPU performance (e.g., Go) can improve speed. Option B is wrong because increasing reserved concurrency does not affect individual function performance. Option D is wrong because Lambda does not support GPU. Option E is wrong because Kinesis batch size does not affect CPU-bound processing.

Answer

Increase the function's reserved concurrency.

Answer

Increase the Kinesis stream's shard count.

Answer

Enable GPU acceleration for the function.

Question 4

A company is using Amazon S3 to store large objects. Users report that uploads are slow. Which THREE actions should the developer take to optimize upload performance?

Accepted Answer

Use multipart upload for objects over 100 MB.. Option A is correct because multipart upload improves performance for large objects. Option B is correct because using S3 Transfer Acceleration reduces latency. Option C is correct because using S3 prefixes increases request rate performance. Option D is wrong because S3 Select is for retrieving subsets of data, not uploads. Option E is wrong because Glacier is for archival, not for active uploads.

Answer

Use S3 Select to upload only specific parts of the object.

Answer

Transition objects to S3 Glacier after upload.

Question 5

A developer runs the AWS CLI command shown in the exhibit. The output includes 'FunctionError': 'Unhandled'. What does this indicate?

Accepted Answer

The function threw an unhandled exception.. Option C is correct because 'Unhandled' means the function returned an error that was not caught by the code. Option A is wrong because StatusCode 200 indicates successful invocation, not failure to invoke. Option B is wrong because a handled error would show 'Handled'. Option D is wrong because a timeout would be a different error.

Answer

The function threw an error that was caught by the code.

Answer

The function timed out.

Answer

The function was not invoked successfully.

Question 6

A developer receives an Access Denied error when trying to download an object from an S3 bucket. The developer's IAM policy is shown in the exhibit. The bucket policy also grants access. What is the MOST likely cause?

Accepted Answer

The S3 bucket uses SSE-KMS and the user lacks kms:Decrypt permission.. Option B is correct because if the bucket is encrypted with a KMS key, the user must also have kms:Decrypt permission. Option A is wrong because the policy explicitly allows s3:GetObject. Option C is wrong because the bucket policy also grants access, so it's not a bucket policy issue. Option D is wrong because public access is not required if IAM policies allow access.

Answer

The S3 bucket has block public access enabled.

Answer

The IAM policy does not allow s3:GetObject.

Answer

The bucket policy denies access to the user.

Question 7

A developer is creating an ECS task definition using the JSON shown in the exhibit. The task fails to run with an error about insufficient memory. What is the issue?

Accepted Answer

The task memory and cpu values are specified as strings instead of integers.. Option A is correct because the container memory (256) plus task memory (512) must be consistent; the task memory is 512 but the container memory is 256, which is okay, but the error indicates the container memory is higher than task memory? Actually, the task memory is 512, container memory 256, so it's fine. However, the exhibit shows task memory as a string '512' and CPU as '256'; they should be integers. Option A is the most likely: the task memory is set to 512 but the container memory is 256, which is less, so that's not an issue. Wait, the error is about insufficient memory. Perhaps the container memory should be equal to task memory? Actually, the error might be because the task memory is not enough for the container? The container memory is 256, task memory 512, so that's fine. Let me reconsider. The exhibit shows 'memory': '512' (string) and 'cpu': '256' (string). In ECS task definition, memory and cpu must be integers, not strings. That could cause the task to fail. Option B is correct: the values are strings. Option A is wrong because container memory is less than task memory. Option C is wrong because container port mapping is valid. Option D is wrong because network mode is not specified, but default is bridge which is fine.

Answer

The container port is not mapped to a host port.

Answer

The task definition does not specify a network mode.

Answer

The container memory is less than the task memory.

Question 8

A developer notices that an Amazon RDS for MySQL DB instance's CPU utilization is consistently above 90% during peak hours. The application uses read-heavy workloads. Which action would MOST effectively reduce CPU load without major architectural changes?

Accepted Answer

Create a Multi-AZ deployment and use the standby for read queries.. Option B is correct because adding a read replica offloads read queries from the primary instance, reducing CPU usage for read-heavy workloads. Option A (increasing instance size) might help but is less cost-effective and does not address read vs write separation. Option C (ElastiCache) adds caching but requires application changes. Option D (Aurora) involves migration effort.

Answer

Implement an in-memory cache layer with Amazon ElastiCache.

Answer

Migrate the database to Amazon Aurora with auto-scaling.

Answer

Increase the DB instance size to a larger instance type.

Question 9

A Lambda function is timing out after 3 seconds when processing an S3 event. The function reads a file from S3 and writes to DynamoDB. The timeout is set to 5 seconds. What is the MOST likely cause of the timeout?

Accepted Answer

The function is attached to a VPC without a NAT gateway, causing network timeouts when accessing S3 and DynamoDB.. Option C is correct because the default Lambda timeout is 3 seconds, and the function's configured timeout (5 seconds) is higher, so it should not timeout at 3 seconds unless the function itself is hanging. However, the stem says 'timing out after 3 seconds' which suggests the function execution is being terminated at 3 seconds. The most common cause is that the function's configured timeout is actually 3 seconds (not 5 as stated). But the stem says 'the timeout is set to 5 seconds', so if it times out at 3, it could be due to a VPC configuration causing network delays. Actually, the most likely cause is that the function is in a VPC without a proper internet gateway or NAT gateway, causing network calls to S3 and DynamoDB to hang. Option C addresses that. Option A (insufficient memory) would cause slower execution but not a hard timeout at exactly 3 seconds. Option B (concurrency limit) would cause throttling, not timeout. Option D (DynamoDB throttling) would cause retries and slower performance but not a hard timeout at 3 seconds.

Answer

DynamoDB write capacity is insufficient, causing write requests to be throttled.

Answer

The function's memory allocation is too low, causing CPU throttling.

Answer

The function is hitting the reserved concurrency limit and being throttled.

Question 10

A developer is troubleshooting an application that uses Amazon SQS. Messages are being sent to a dead-letter queue (DLQ) after the maximum receive count is exceeded. The consumer processes messages but sometimes fails. The developer wants to ensure that messages are retried immediately after a failure, without waiting for the visibility timeout. Which solution should the developer implement?

Accepted Answer

After a failure, call ChangeMessageVisibility with a timeout of 0 to make the message immediately available for reprocessing.. Option D is correct because calling ChangeMessageVisibility with a timeout of 0 makes the message immediately visible to other consumers for retry. Option A (delete and re-send) would create a new message with a new message ID, losing the original message attributes. Option B (increase visibility timeout) would delay retry. Option C (delay queue) would add a delay before the message becomes available, which is opposite of what is needed.

Answer

Configure a delay queue so that messages are not immediately visible after failure.

Answer

Delete the message from the queue and re-send it after processing failure.

Answer

Increase the visibility timeout to allow more time for processing.

Question 11

A developer is using AWS CodeBuild to build a Java application. The build succeeds locally but fails on CodeBuild with a 'Cannot find symbol' error for a class that is in a dependency JAR. What is the MOST likely cause?

Accepted Answer

The dependency cache is not enabled in CodeBuild, so dependencies are not available.. Option C is correct because CodeBuild by default does not include cached dependencies; each build downloads dependencies from scratch unless a cache is configured. The local build works because Maven/Gradle caches dependencies locally. Option A (buildspec syntax) would cause a different error. Option B (build timeout) would cause a timeout, not a compilation error. Option D (insufficient compute) would cause performance issues but not a missing symbol.

Answer

The build is timing out before dependencies are fully downloaded.

Answer

The CodeBuild compute type does not have enough memory to compile the project.

Answer

The buildspec file has incorrect syntax causing the build to skip dependency resolution.

Question 12

An application running on Amazon ECS Fargate is experiencing intermittent high latency and timeout errors. The application makes API calls to an external third-party service. The ECS service is configured with a target group using HTTP health checks. The ALB health check logs show occasional 503 responses. What is the MOST likely cause?

Accepted Answer

The application is not properly handling timeouts to the third-party service, causing the health check endpoint to hang.. Option A is correct because if the application is waiting for a response from the third-party service, it may not respond to health checks in time, causing the ALB to mark it unhealthy and stop routing traffic, which exacerbates the issue. Option B (insufficient CPU) could cause latency but not specifically 503s. Option C (security group) would cause consistent failures. Option D (task placement) would cause new tasks to be created, but not 503s.

Answer

The security group for the ECS tasks is blocking inbound traffic from the ALB.

Answer

The ECS tasks are running out of CPU credits, causing slow response times.

Answer

The ECS service is configured with a task placement strategy that is causing tasks to be stopped and restarted frequently.

Question 13

A developer is using AWS CloudFormation to deploy a stack. The stack creation fails with the error 'API: iam:CreateRole User: arn:aws:iam::123456789012:user/DevUser is not authorized to perform: iam:CreateRole'. The developer is using an IAM user with AdministratorAccess policy attached. What is the MOST likely cause of this error?

Accepted Answer

The CloudFormation stack is using a service role that does not have iam:CreateRole permission.. Option D is correct because CloudFormation uses a service role to create resources if a service role is specified. If the service role does not have the necessary permissions, the stack creation will fail even if the user has full permissions. Option A (region issue) is not relevant. Option B (resource limit) would give a limit exceeded error. Option C (policy version) would not cause this specific error.

Answer

The account has reached the IAM role limit.

Answer

The CloudFormation stack is being created in a region where IAM is not supported.

Answer

The AdministratorAccess policy has been modified to remove IAM permissions.

Question 14

A developer deployed a new version of a Lambda function using an alias that points to the new version. However, the function continues to invoke the old version. What is the MOST likely cause?

Accepted Answer

The alias was not updated to point to the new version after deployment.. Option B is correct because if the version number in the alias is not updated, the alias still points to the old version. Option A (concurrency) does not affect which version is invoked. Option C (different function name) would cause a different error. Option D (IAM permissions) would cause access denied errors, not invocation of old code.

Answer

The IAM execution role for the Lambda function does not have permission to invoke the new version.

Answer

The Lambda function's reserved concurrency is set to 0, preventing new invocations.

Answer

The function name in the invocation request is different from the deployed function.

Question 15

A company uses Amazon S3 to store sensitive data. A developer needs to ensure that all objects uploaded to a specific S3 bucket are encrypted at rest. Which approach should the developer take?

Accepted Answer

Add a bucket policy that denies PutObject if the object is not encrypted.. Option D is correct because using a bucket policy that denies PutObject if the object is not encrypted with SSE-S3, SSE-KMS, or SSE-C ensures encryption is enforced. Option A (default encryption) encrypts objects that don't have encryption specified, but it does not prevent unencrypted uploads if the client overrides. Option B (IAM policy) is cumbersome and not bucket-specific. Option C (pre-signed URLs) does not enforce encryption.

Answer

Use pre-signed URLs with server-side encryption parameters.

Answer

Attach an IAM policy to all users requiring them to include the x-amz-server-side-encryption header.

Answer

Enable default encryption on the bucket using SSE-S3.