DVA-C02 Practice Test 34 — 15 Questions

Question 1

An organization has a Lambda function that processes messages from an Amazon SQS queue. The function is configured with a reserved concurrency of 5. The SQS queue has a visibility timeout of 30 seconds. The Lambda function takes an average of 45 seconds to process each message. What is the likely behavior of this setup?

Accepted Answer

Messages will be processed multiple times because they become visible again before the function completes.. Option C is correct because the Lambda function takes longer than the visibility timeout, causing messages to become visible again before processing completes. This leads to duplicate processing. Option A is wrong because Lambda will still process the message even if it takes longer. Option B is wrong because the reserved concurrency limit may cause throttling but not duplication. Option D is wrong because messages are not deleted until the function completes, so they become visible again.

Answer

The Lambda function will be throttled due to reserved concurrency.

Answer

The Lambda function will process messages successfully with no issues.

Answer

The Lambda function will automatically increase its processing speed.

Question 2

A developer is using API Gateway to expose a Lambda function as a REST API. The API must be accessible from a web application hosted on a different domain. The developer configured CORS but the browser still shows CORS errors. What should the developer do to resolve the issue?

Accepted Answer

Enable CORS in API Gateway and ensure the OPTIONS method returns the required headers.. API Gateway requires explicit CORS configuration including OPTIONS method. Option D is correct. Option A is irrelevant. Option B is not enough without enabling CORS. Option C is incorrect because Lambda does not handle CORS for API Gateway.

Answer

Configure the Lambda function to return HTTP 200 for preflight OPTIONS requests.

Answer

Set the Access-Control-Allow-Origin header in the Lambda function response.

Answer

Add the web application's domain to an API Gateway usage plan.

Question 3

Refer to the exhibit. A developer invokes a Lambda function using the AWS CLI. The response shows StatusCode 200 and FunctionError: Unhandled. What does this indicate?

Accepted Answer

The Lambda function threw an exception that was not caught by the code.. FunctionError: Unhandled means the function threw an exception. Option C is correct. Option A is wrong because StatusCode 200 indicates invocation succeeded but function failed. Option B is wrong because function did execute. Option D is wrong because response is not an error from CLI.

Answer

The Lambda function timed out before completing.

Answer

The Lambda function executed successfully without errors.

Answer

The AWS CLI failed to invoke the function due to permissions.

Question 4

A developer is building a real-time chat application using WebSocket APIs in API Gateway and Lambda. The application must handle thousands of concurrent connections. Which TWO actions should the developer take to ensure the application scales properly?

Accepted Answer

Set the Lambda function's reserved concurrency to a high enough value.. Options B and C are correct. Using a DynamoDB table to store connection IDs (B) is a common pattern for managing WebSocket connections. Setting the Lambda function concurrency limit (C) prevents throttling of other functions. Option A is wrong because Lambda functions in a VPC have limited elastic network interfaces. Option D is wrong because API Gateway handles scaling automatically. Option E is wrong because CloudFront does not support WebSocket APIs.

Answer

Use CloudFront to distribute the WebSocket endpoints.

Answer

Place the Lambda function in a VPC to improve security.

Answer

Enable API Gateway caching to reduce Lambda invocations.

Question 5

A developer is using AWS CodePipeline to automate the deployment of a web application. The developer wants to run unit tests after the source stage and before deploying to a staging environment. Which action should the developer add to the pipeline?

Accepted Answer

AWS CodeBuild. Option B is correct because AWS CodeBuild is a build service that can run unit tests. Option A is wrong because CodeDeploy deploys, does not test. Option C is wrong because CodeCommit is a source repository. Option D is wrong because CloudFormation is for infrastructure provisioning.

Answer

AWS CodeCommit

Answer

AWS CloudFormation

Answer

AWS CodeDeploy

Question 6

A developer is using AWS CodePipeline to automate CI/CD. The pipeline has a Source stage (CodeCommit), a Build stage (CodeBuild), and a Deploy stage (CodeDeploy). The Build stage runs tests and packages the application. The developer notices that the Deploy stage is triggered even when the Build stage fails. How can the developer prevent deployment on build failure?

Accepted Answer

Configure the Build stage with 'On failure: Abort' in the pipeline settings.. CodePipeline transitions automatically unless a stage fails. Option A is correct because setting 'On failure: Abort' will stop the pipeline. Option B is incorrect because notifications do not prevent transition. Option C is incorrect because transitions are between stages, not within. Option D is incorrect because manual approval is not automatic.

Answer

Set a transition between Build and Deploy stages that only allows successful builds.

Answer

Add a manual approval action before Deploy stage.

Answer

Add a CloudWatch Events rule to trigger a Lambda function that stops the pipeline on build failure.

Question 7

A company is using AWS Lambda with a 1 GB memory configuration. The function processes large CSV files from S3 and occasionally times out after 15 seconds. The function currently uses synchronous invocation. What is the MOST cost-effective solution to handle larger files without losing data?

Accepted Answer

Increase the Lambda timeout to 15 minutes and keep memory at 1 GB.. Option B is correct because increasing the Lambda timeout up to 15 minutes (the maximum for synchronous invocation) and keeping memory at 1 GB is cost-effective. Option A is wrong because increasing memory also increases cost without guaranteeing timeout resolution. Option C is wrong because asynchronous invocation has a 15-minute timeout but may not be suitable for all use cases. Option D is wrong because Step Functions add complexity and cost.

Answer

Switch to asynchronous Lambda invocation to allow up to 15 minutes of processing.

Answer

Increase the Lambda memory to 3 GB to improve processing speed.

Answer

Use AWS Step Functions to orchestrate the processing in smaller chunks.

Question 8

A developer is designing a serverless application that processes orders. The order processing must be transactional: either all steps succeed or none. Which TWO AWS services can be combined to achieve this?

Accepted Answer

AWS Step Functions. Options B and D are correct. Step Functions (B) can orchestrate a workflow with error handling and rollback. DynamoDB transactions (D) provide ACID transactions for multiple items. Option A is wrong because SQS does not provide transactional processing. Option C is wrong because Lambda alone does not manage transactions across multiple steps. Option E is wrong because SNS is for pub/sub messaging, not transactions.

Answer

Amazon SNS with filtering

Answer

Amazon SQS with FIFO queues

Answer

AWS Lambda with DLQ

Question 9

A developer is designing a serverless application that uses Amazon API Gateway and AWS Lambda. The application needs to handle a sudden spike in traffic. The Lambda function performs CPU-intensive operations. What should the developer do to ensure the application scales without errors?

Accepted Answer

Configure the Lambda function with reserved concurrency and provisioned concurrency.. Option C is correct because Lambda concurrency limits control scaling, and provisioned concurrency prevents cold starts. Option A is wrong because API Gateway throttling would reject requests. Option B is wrong because increasing timeout doesn't help scaling. Option D is wrong because reserved concurrency sets a limit, not a guarantee.

Answer

Set the API Gateway throttling limits to a high value.

Answer

Use an Amazon SQS queue to buffer requests before processing.

Answer

Increase the Lambda function timeout to the maximum value.

Question 10

A developer is using Amazon S3 to host a static website. The website uses JavaScript to fetch data from an API Gateway endpoint. Users report that the website loads but API calls fail with HTTP 403 errors. The developer checks the S3 bucket policy and finds it allows public read access. What is the most likely cause?

Accepted Answer

The S3 bucket does not have CORS configuration to allow cross-origin requests from the API Gateway domain.. S3 static website hosting does not support CORS by default. Option C is correct. Option A is incorrect because S3 bucket policy allows read. Option B is incorrect if bucket policy is correct. Option D is incorrect because authentication is not required for public content.

Answer

The S3 bucket policy blocks access from the API Gateway domain.

Answer

The S3 bucket is not configured for static website hosting.

Answer

The API Gateway API key is not included in the JavaScript code.

Question 11

An application running on Amazon ECS Fargate uses a DynamoDB table with on-demand capacity. The table has a partition key of 'userId' and a sort key of 'timestamp'. During peak hours, some requests experience throttling errors. The application performs updates to existing items using 'UpdateItem' with ConditionExpression to ensure the 'status' attribute is 'active'. Which design change will BEST reduce throttling?

Accepted Answer

Implement DynamoDB Accelerator (DAX) to cache frequent items.. Option D is correct because using DynamoDB Accelerator (DAX) can reduce throttling by offloading read requests from the table, allowing on-demand capacity to handle write-heavy workloads. Option A is wrong because increasing read capacity is not applicable to on-demand tables. Option B is wrong because 'UpdateItem' with ConditionExpression already performs atomic updates. Option C is wrong because sparse indexes do not help with throttling.

Answer

Use 'TransactWriteItems' instead of 'UpdateItem' for atomic updates.

Answer

Change the table to provisioned capacity and increase read capacity units.

Answer

Create a global secondary index with the same partition key and a different sort key.

Question 12

A company is building a serverless application using AWS Lambda functions that write results to an Amazon DynamoDB table. The Lambda functions are invoked by an Amazon API Gateway REST API. During testing, some requests fail with a 503 status code. The Lambda function code is correct. What is the MOST likely cause of the 503 errors?

Accepted Answer

The Lambda function execution time exceeds the configured timeout.. Option B is correct because 503 errors from API Gateway typically indicate that the Lambda function is not returning a response within the timeout. Option A is wrong because DynamoDB writes are asynchronous from API Gateway's perspective. Option C is wrong because missing IAM role would cause 500 or 403, not 503. Option D is wrong because throttling would cause 429, not 503.

Answer

The DynamoDB table has insufficient write capacity.

Answer

The Lambda function's IAM role does not have permission to write to DynamoDB.

Answer

The API Gateway stage has throttling limits configured.

Question 13

A company is using AWS CloudFormation to deploy infrastructure. The developer needs to update a stack but wants to avoid downtime for a critical database. Which THREE strategies should the developer consider?

Accepted Answer

Use the UpdateReplace policy to create a new resource before deleting the old one.. Option A (Change sets) is correct because they allow previewing changes. Option B (Stack policy) is correct because it can protect specific resources during updates. Option D (UpdateReplace policy) is correct because it can create a replacement before deletion. Option C is wrong because deletion policy is about stack deletion, not updates. Option E is wrong because it's a parameter, not a strategy.

Answer

Set the DeletionPolicy attribute to Retain on the database resource.

Answer

Use the Parameters section to set a conditional update flag.

Question 14

An application running on Amazon EC2 instances in an Auto Scaling group processes messages from an SQS queue. The application runs in a private subnet and needs to send metrics to Amazon CloudWatch. How can the developer ensure the EC2 instances can send metrics without traversing the internet?

Accepted Answer

Create a VPC Endpoint for CloudWatch (com.amazonaws.region.monitoring).. VPC Endpoint for CloudWatch allows private connectivity. Option D is correct. Option A (NAT Gateway) requires internet. Option B (Internet Gateway) is public. Option C (CloudWatch Agent) can send but still needs network path; endpoint is the solution.

Answer

Attach a NAT Gateway to the private subnet and update the route table.

Answer

Install the CloudWatch agent on each instance and configure it to use a proxy.

Answer

Attach an Internet Gateway to the VPC and assign public IPs to instances.

Question 15

A developer is using AWS SAM to deploy a serverless application. The template includes a Lambda function that connects to an RDS MySQL database. The function works correctly in the developer's account but fails with a timeout when deployed to a production account. What is the MOST likely cause?

Accepted Answer

The Lambda function is not attached to the same VPC as the RDS instance.. Option B is correct because the Lambda function may not have a VPC configuration to access the RDS database in the production account. Option A is wrong because SAM supports RDS connections. Option C is wrong because Lambda's default timeout is 3 seconds, but the function may have a higher timeout set. Option D is wrong because Lambda supports Python natively.

Answer

The Lambda function timeout is set too low for the database query.

Answer

The SAM template does not support RDS as an event source.

Answer

The Lambda function uses a runtime that is not compatible with the MySQL client.