DVA-C02 Development with AWS Services Practice Test 29 — 15 Questions

Question 1

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 2

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 3

A company uses AWS CodePipeline to deploy a web application to an EC2 instance. The deployment often fails because the application is still running when new files are copied. Which THREE actions can be combined to achieve zero-downtime deployments?

Accepted Answer

Use AWS CodeDeploy with an in-place deployment configuration.. Options A, B, and D are correct. Using CodeDeploy (A) with an in-place deployment can manage the lifecycle. The AppSpec file (B) can define hooks to stop the application before install and start it after. Auto Scaling group (D) with a rolling update can ensure instances are replaced without downtime. Option C is wrong because CodeBuild is for building, not deployment. Option E is wrong because Amazon Inspector is for security scanning.

Answer

Use AWS CodeBuild to build and deploy the application.

Answer

Use Amazon Inspector to check the application before deployment.

Question 4

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 5

A developer wants to upload a large file (5 GB) to an Amazon S3 bucket using the AWS SDK. Which approach is MOST efficient and resilient?

Accepted Answer

Use the Multipart Upload API to upload the file in parts.. Option C is correct because the S3 Multipart Upload API is designed for large objects, providing better throughput and resilience. Option A is wrong because it does not support objects over 5 GB. Option B is wrong because presigned URLs don't provide multipart upload benefits. Option D is wrong because Lambda has a payload limit.

Answer

Generate a presigned URL and use a third-party tool to upload.

Answer

Invoke an AWS Lambda function to upload the file.

Answer

Use the PutObject API call with the entire file.

Question 6

A developer is deploying a microservices architecture on Amazon ECS with Fargate. Each service needs to store sensitive configuration data such as database passwords. The developer wants to avoid hardcoding secrets in the application code. Which approach should the developer use?

Accepted Answer

Store the secrets in AWS Systems Manager Parameter Store or AWS Secrets Manager and reference them in the ECS task definition using the 'secrets' parameter.. Option A is correct because AWS Systems Manager Parameter Store or AWS Secrets Manager can securely store secrets and be referenced in ECS task definitions. Option B is wrong because environment variables in the task definition are visible in plaintext. Option C is wrong because S3 is not designed for secrets. Option D is wrong because it increases attack surface.

Answer

Store the secrets in an Amazon S3 bucket and use a pre-signed URL to download them at startup.

Answer

Define the secrets as environment variables in the ECS task definition.

Answer

Encrypt the secrets using AWS KMS and store the encrypted blob in a configuration file within the Docker image.

Question 7

A company is using Amazon CloudFront to serve content from an Application Load Balancer (ALB) origin. The ALB is configured as an internal load balancer in a VPC. Users are getting HTTP 502 errors when accessing the CloudFront distribution. What is the MOST likely cause?

Accepted Answer

The ALB is not internet-facing, so CloudFront cannot reach it.. Option D is correct because CloudFront cannot reach an internal ALB unless it is internet-facing. Option A is wrong because CloudFront does not need a VPN. Option B is wrong because WAF does not cause 502 errors. Option C is wrong because content caching does not cause 502.

Answer

The ALB has AWS WAF enabled, blocking CloudFront IP addresses.

Answer

The CloudFront distribution's cache behavior is set to cache all objects.

Answer

The CloudFront distribution is not associated with a VPN connection to the VPC.

Question 8

A developer needs to analyze real-time streaming data from thousands of devices. The data consists of JSON messages that must be processed and stored in Amazon S3. Which AWS service should the developer use to ingest and buffer the streaming data?

Accepted Answer

Amazon Kinesis Data Streams. Option A is correct because Amazon Kinesis Data Streams is designed for real-time data ingestion and can buffer data. Option B is wrong because Lambda is for compute, not ingestion. Option C is wrong because SQS is for message queues, not high-throughput streaming. Option D is wrong because S3 is storage, not ingestion.

Answer

Amazon S3

Answer

AWS Lambda

Answer

Amazon Simple Queue Service (SQS)

Question 9

A developer is building an application that uses Amazon DynamoDB as a data store. The application reads the same item frequently but writes rarely. The developer wants to reduce read costs. Which DynamoDB feature should the developer use?

Accepted Answer

DynamoDB Accelerator (DAX). Option B is correct because DynamoDB Accelerator (DAX) is an in-memory cache that reduces read costs for frequently accessed items. Option A is wrong because auto scaling adjusts capacity, not cost per read. Option C is wrong because TTL is for automatic deletion. Option D is wrong because Global Tables are for multi-region replication, not cost reduction.

Answer

DynamoDB Global Tables

Answer

DynamoDB Auto Scaling

Answer

Time to Live (TTL)

Question 10

A company has an AWS Lambda function that processes messages from an Amazon SQS queue. The function sometimes fails due to transient errors. The developer wants to ensure that failed messages are retried automatically and then sent to a dead-letter queue after three failed attempts. How should the developer configure this?

Accepted Answer

Configure the SQS queue with a redrive policy and a dead-letter queue. Set the maxReceiveCount to 3.. Option A is correct because SQS redrive policy and dead-letter queue handle retries and failures. Option B is wrong because Lambda's retry is separate. Option C is wrong because DLQ on Lambda doesn't integrate with SQS retry logic. Option D is wrong because Lambda destination is for success/failure, not retries.

Answer

Enable Lambda function's DLQ and set the retry attempts to 3.

Answer

Configure the Lambda function's reserved concurrency to 0 and set the DLQ on the function.

Answer

Use an Amazon SNS topic to send failed messages to a DLQ after three Lambda invocations.

Question 11

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 12

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 13

A developer is designing a mobile application that needs to upload files to Amazon S3. The developer wants to use temporary credentials to avoid storing long-term AWS credentials on the device. Which TWO services should the developer use together?

Accepted Answer

AWS Security Token Service (STS). Option A (Amazon Cognito) is correct because it provides identity pools for temporary AWS credentials. Option D (AWS STS) is correct because it issues temporary credentials. Option B is wrong because IAM is for long-term users. Option C is wrong because KMS is for encryption. Option E is wrong because S3 Transfer Acceleration is for speed.

Answer

Amazon S3 Transfer Acceleration

Answer

AWS Identity and Access Management (IAM)

Answer

AWS Key Management Service (KMS)

Question 14

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 15

A developer is troubleshooting an AWS Lambda function that is invoked by an Amazon S3 bucket notification. The function processes new objects but sometimes fails because the object is not fully written before Lambda reads it. Which TWO actions can the developer take to fix this?

Accepted Answer

Implement a retry mechanism in the Lambda function to check object existence before processing.. Option A (S3 event notification with suffix) is correct because it can target specific file types that are written last. Option D (Retry logic) is correct because it handles eventual consistency. Option B is wrong because SQS doesn't solve the write-in-progress issue. Option C is wrong because it doesn't help. Option E is wrong because it doesn't address the timing.

Answer

Use S3 Transfer Acceleration.

Answer

Use an Amazon SQS queue to buffer the S3 events.

Answer

Increase the Lambda function timeout.