DVA-C02 Practice Test 15 — 15 Questions

Question 1

A developer is building a real-time chat application using Amazon API Gateway WebSockets and AWS Lambda. The developer notices that messages are sometimes delivered out of order. What should the developer do to ensure ordered message delivery?

Accepted Answer

Use an Amazon SQS FIFO queue to buffer messages before processing. WebSocket connections are stateful; using a FIFO queue ensures ordering. Option C is correct.

Answer

Increase the Lambda function's memory allocation

Answer

Use API Gateway's built-in message ordering feature

Answer

Set the 'sequenceNumber' property in the WebSocket message

Question 2

The exhibit shows an IAM policy attached to a user. The user reports being unable to upload files to S3 bucket 'my-bucket'. What is the MOST likely cause?

Accepted Answer

The bucket policy denies the upload. The PutObject action requires s3:PutObject permission, which is granted. However, the bucket may have a bucket policy that denies the upload. Option D is correct.

Answer

The user needs s3:PutObjectAcl permission

Answer

The policy does not allow s3:ListBucket

Answer

The user does not have s3:GetObject permission

Question 3

A developer is deploying an application using AWS Elastic Beanstalk. The application reads and writes data to an Amazon RDS database. The developer wants to ensure that database credentials are not stored in the application code or configuration files. What should the developer do?

Accepted Answer

Store the credentials as environment properties in the Elastic Beanstalk environment configuration.. Option D is correct because Elastic Beanstalk can pass environment properties securely by storing them in the EB environment configuration, and they can be retrieved at runtime. Option A is wrong because hardcoding in environment variables in the EB console is not secure; they can be seen in the console. Option B is wrong because storing credentials in S3 and downloading them adds complexity and potential exposure. Option C is wrong because Secrets Manager is a good practice, but Elastic Beanstalk can inject secrets as environment properties without custom code.

Answer

Encrypt the credentials and store them in an Amazon S3 bucket. Have the application download them at startup.

Answer

Use AWS Secrets Manager to store the credentials and retrieve them in the application code.

Answer

Store the credentials in a separate configuration file and include it in the application source bundle.

Question 4

A developer is designing a serverless application that uses Amazon DynamoDB as the data store. The application must handle sudden spikes in read traffic without throttling. Which THREE actions should the developer take?

Accepted Answer

Configure DynamoDB auto scaling for the table. DAX provides caching for reads, DynamoDB auto scaling adjusts capacity, and exponential backoff handles throttling gracefully. Options A, C, and D are correct.

Answer

Use a global secondary index with a different partition key

Answer

Use strongly consistent reads for all queries

Question 5

A developer is building a serverless application using AWS Lambda functions that process events from Amazon SQS. The developer notices that some messages are being processed multiple times. What is the MOST likely cause of this issue?

Accepted Answer

The SQS visibility timeout is too short for the Lambda function's execution time.. Option A is correct because Lambda's SQS event source mapping uses long polling and may receive a message, then the visibility timeout expires before processing completes, causing the message to become visible again. Option B is wrong because dead-letter queues do not cause duplication. Option C is wrong because Lambda functions process one message at a time by default from SQS. Option D is wrong because reserved concurrency limits concurrency, not duplication.

Answer

The Lambda function's reserved concurrency is set too high.

Answer

The SQS queue has a dead-letter queue configured.

Answer

The Lambda function's batch size is set to more than 1.

Question 6

A company runs a critical web application on Amazon EC2 instances behind an Application Load Balancer. The application needs to authenticate users via an external OpenID Connect (OIDC) identity provider. The company wants to offload authentication to the load balancer and use IAM roles to access AWS resources. Which solution should the developer implement?

Accepted Answer

Configure the ALB to use the OIDC identity provider for user authentication. Use the identity token to assume an IAM role via web identity federation.. Option B is correct because ALB can authenticate users via OIDC and pass the user's identity to the application via HTTP headers. The application can then use the token to assume an IAM role using web identity federation. Option A is wrong because Cognito is not required; ALB supports OIDC directly. Option C is wrong because Lambda@Edge is for CloudFront, not ALB. Option D is wrong because ALB does not support OIDC directly with just a target group; authentication is configured on the listener rule.

Answer

Configure the ALB target group to authenticate using the OIDC identity provider.

Answer

Use AWS Lambda@Edge to authenticate users at the edge.

Answer

Use Amazon Cognito user pools as the OIDC provider and integrate with ALB.

Question 7

The exhibit shows the output of a command. What does this output indicate about the bucket?

Accepted Answer

Versioning is enabled, and MFA delete is not required. Versioning is enabled, but MFA delete is not required. Option B is correct.

Answer

Versioning is enabled, and MFA delete is required

Answer

Versioning is suspended

Answer

Versioning is disabled

Question 8

A developer is writing an AWS Lambda function in Python that needs to download a file from Amazon S3, process it, and upload the result to a different S3 bucket. The function currently runs within the default 3-second timeout, but the developer expects the file size to increase. What is the MOST cost-effective way to handle the increase in processing time?

Accepted Answer

Increase the Lambda function's timeout to a value higher than the expected processing time.. Option C is correct because increasing the Lambda timeout is the simplest and most cost-effective way to handle longer processing times. Option A is wrong because Step Functions add cost and complexity. Option B is wrong because Lambda functions cannot run longer than 15 minutes. Option D is wrong because provisioned concurrency is for reducing cold starts, not for extending timeout.

Answer

Increase the Lambda function's timeout to 15 minutes.

Answer

Use Lambda provisioned concurrency to keep the function warm.

Answer

Refactor the code to use AWS Step Functions to orchestrate the processing.

Question 9

A developer runs the query shown in the exhibit on a DynamoDB table named 'Orders' and gets an error. What is the MOST likely cause?

Accepted Answer

The table's partition key is not named 'OrderID'. The Query operation requires a partition key; the error indicates that OrderID is not the partition key. Option B is correct.

Answer

The expression attribute values are incorrectly formatted

Answer

The table does not exist

Answer

The query needs to use a sort key

Question 10

A developer is building a real-time chat application using Amazon API Gateway WebSocket APIs and AWS Lambda. The application needs to send messages to connected clients. The developer notices that the 'connectionId' changes every time a client reconnects. How should the developer store the mapping between user identity and connectionId?

Accepted Answer

Use Amazon DynamoDB to store the mapping, with user identity as the partition key and connectionId as an attribute.. Option A is correct because DynamoDB provides fast, scalable storage for the connectionId mapping. Option B is wrong because ElastiCache is ephemeral and not ideal for persistence. Option C is wrong because S3 is not designed for low-latency lookups. Option D is wrong because RDS adds overhead and cost for this simple use case.

Answer

Use Amazon ElastiCache to store the mapping in memory.

Answer

Use Amazon RDS to store the mapping in a relational database.

Answer

Use Amazon S3 to store the mapping as a JSON file.

Question 11

A developer is using Amazon API Gateway to expose a Lambda function as a REST API. The API should only be accessible from a specific VPC. Which TWO steps are required to achieve this? (Choose TWO.)

Accepted Answer

Create a VPC endpoint for API Gateway.. Option B is correct because a resource policy on API Gateway can restrict access to a VPC. Option E is correct because a VPC endpoint for API Gateway allows API Gateway to receive traffic from the VPC privately. Option A is wrong because Lambda VPC configuration is for the function's access to VPC resources, not for API Gateway. Option C is wrong because a VPC endpoint for Lambda is not needed for API Gateway access. Option D is wrong because an API key is for authentication, not network restriction.

Answer

Use an API key that is only known within the VPC.

Answer

Configure the Lambda function to be VPC-enabled.

Answer

Create a VPC endpoint for Lambda.

Question 12

A company uses AWS CodeBuild to run unit tests. The buildspec.yml file is stored in the source repository. The build fails intermittently with 'command not found' for a tool that is installed in the build environment. What should the developer do to ensure the tool is available?

Accepted Answer

Add a pre_build phase to install the tool.. Option A is correct because CodeBuild supports installing dependencies in the pre_build phase. Option B is wrong because phases are already defined. Option C is wrong because the tool may not be available in all environments. Option D is wrong because CodeBuild environments are not customizable via console.

Answer

Use a custom Docker image that includes the tool.

Answer

Configure the build environment to include the tool via the AWS Management Console.

Answer

Add a post_build phase to install the tool.

Question 13

A developer is using Amazon DynamoDB with provisioned throughput. The application is receiving ProvisionedThroughputExceededException errors. What is the BEST way to handle this error?

Accepted Answer

Implement exponential backoff and retry in the application code.. Option D is correct because the best practice is to implement exponential backoff and retry logic. Option A is wrong because the error is transient, not a permanent issue. Option B is wrong because switching to on-demand would resolve the issue but is not the best way to handle the error; it's a capacity change, not an error handling strategy. Option C is wrong because reducing read capacity would make the problem worse.

Answer

Contact AWS Support to increase the DynamoDB service limits.

Answer

Reduce the read and write capacity units.

Answer

Switch the table to on-demand capacity mode.

Question 14

A developer is building a data processing pipeline that uses Amazon Kinesis Data Streams. The developer wants to ensure that records are processed in order within each shard. The consumer application runs on Amazon EC2 instances in an Auto Scaling group. What should the developer do to maintain ordering?

Accepted Answer

Ensure that one consumer processes each shard exclusively.. Option D is correct because each shard's records have a sequence number, and a single consumer can process them in order. Option A is wrong because multiple consumers in a group can process different shards but ordering within a shard is maintained only if one consumer handles that shard. Option B is wrong because DynamoDB streams are for DynamoDB tables, not Kinesis. Option C is wrong because Lambda consumes records in batches, but ordering is preserved within a shard as long as there's only one concurrent invocation per shard. However, the best practice is to have one consumer per shard.

Answer

Use Amazon DynamoDB Streams to capture the order.

Answer

Use AWS Lambda as the consumer and set the batch size to 1.

Answer

Use the Kinesis Client Library (KCL) with multiple workers in the same consumer group.

Question 15

A company runs a microservices architecture on Amazon ECS with Fargate. The application experiences intermittent high latency. The operations team wants to trace requests across services and identify bottlenecks. Which AWS service should be used?

Accepted Answer

AWS X-Ray. Option B is correct because AWS X-Ray provides end-to-end tracing for distributed applications. Option A is wrong because CloudWatch Logs only collects logs, not traces. Option C is wrong because CloudWatch Metrics provides aggregated metrics but not request-level traces. Option D is wrong because VPC Flow Logs capture network metadata but not application-level tracing.

Answer

VPC Flow Logs

Answer

Amazon CloudWatch Logs

Answer

Amazon CloudWatch Metrics