DVA-C02 Practice Test 26 — 15 Questions

Question 1

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?

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

Configure the Lambda function with reserved concurrency and provisioned concurrency.. Reserved concurrency guarantees that the Lambda function has a dedicated pool of concurrency available to handle traffic spikes without being throttled by other functions in the account, while provisioned concurrency pre-warms execution environments to eliminate cold starts for CPU-intensive operations. This combination ensures that the application scales smoothly under sudden load without encountering Lambda throttling errors (HTTP 429) or latency spikes from cold starts.

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Set the API Gateway throttling limits to a high value.

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Use an Amazon SQS queue to buffer requests before processing.

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Increase the Lambda function timeout to the maximum value.

Question 2

A developer is optimizing a Node.js Lambda function that processes CSV files from S3. The function reads the entire file into memory, processes it, and writes results to DynamoDB. For large files, the function runs out of memory. What is the MOST effective optimization?

Accepted Answer

Use the AWS SDK's S3 GetObject with a stream and process in chunks.. Using the AWS SDK's S3 GetObject with a stream allows the function to process the CSV file in chunks, avoiding loading the entire file into memory. This directly addresses the memory issue for large files. Option A is incorrect because increasing timeout does not reduce memory usage. Option B is incorrect because while increasing memory might help, it does not solve the root cause and may increase costs; streaming is more efficient. Option D is incorrect because S3 Select is used to filter columns from S3 objects using SQL, but it does not solve the problem of loading the entire file into memory; it could reduce the data transferred but the function still needs to handle streaming or chunking.

Answer

Increase the Lambda timeout to allow more processing time.

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Increase the Lambda function memory to 3008 MB.

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Use S3 Select to retrieve only necessary columns.

Question 3

A developer is using AWS Secrets Manager to store database credentials. The application runs on EC2 and needs to retrieve the secret. Which approach is the most secure?

Accepted Answer

Use an IAM role attached to the EC2 instance with permissions to access the secret, and call the AWS SDK to retrieve it at runtime.. It follows the principle of least privilege and avoids hardcoding or storing secrets in insecure locations. By attaching an IAM role to the EC2 instance, the application can securely retrieve the secret from AWS Secrets Manager at runtime using the AWS SDK, without ever exposing the secret in code, configuration files, or environment variables. This approach leverages IAM's temporary credentials from the instance metadata service (IMDS) to authenticate the SDK call, ensuring the secret is never persisted locally.

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Store the secret in an environment variable in the user data script.

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Retrieve the secret at application startup and store it in a configuration file.

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Download the secret from an S3 bucket using pre-signed URLs.

Question 4

A developer is building a REST API using Amazon API Gateway that will serve static content from an Amazon S3 bucket. The API should cache responses for frequently accessed objects to reduce latency. Which API Gateway feature should the developer enable?

Accepted Answer

API Gateway caching with TTL set per method.. API Gateway caching allows you to cache responses from your backend (e.g., an S3 bucket) for a specified Time-to-Live (TTL) per method, reducing the number of calls to the backend and lowering latency for frequently accessed objects. This feature is natively integrated with API Gateway and requires no additional services or complex configurations, making it the most direct solution for caching static content served through a REST API.

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Amazon CloudFront as a custom domain.

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Lambda@Edge for caching.

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S3 Transfer Acceleration.

Question 5

A developer is using AWS Lambda with an Amazon RDS MySQL database. The Lambda function frequently times out when connecting to the database. What is the MOST likely cause?

Accepted Answer

The Lambda function is not attached to the same VPC as the RDS instance. Lambda functions must be attached to the same VPC as the RDS instance to connect via a private IP address. Without VPC attachment, the Lambda function attempts to connect over the public internet, which can cause timeouts due to network latency, security group restrictions, or the RDS instance being configured as publicly inaccessible.

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The Lambda function is not configured with enough memory

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The Lambda function is not using a reserved concurrency limit

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The Lambda function's execution role lacks RDS permissions

Question 6

A company uses AWS OpsWorks for configuration management. They have a stack with multiple layers. They want to deploy a new application version to the application layer using rolling updates. What is the correct way to achieve this?

Accepted Answer

Update the app with the new version and run the 'deploy' command on the stack.. In AWS OpsWorks, deploying a new application version to a layer is done by updating the app configuration with the new version and then running the 'deploy' command on the stack. This command triggers the built-in Chef deploy recipes on the layer's instances, performing a rolling update that installs the new application version while minimizing downtime. The 'deploy' lifecycle event is specifically designed for application deployment, unlike 'setup' which configures the instance's initial state.

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Update the custom cookbook and run the 'setup' command on the layer.

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Clone the stack and then delete the old stack.

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Modify the Auto Scaling group to launch new instances with the updated app.

Question 7

A development team is building a real-time chat application using Amazon API Gateway WebSocket APIs and AWS Lambda. The application needs to maintain a connection to each user and broadcast messages to all connected clients. Which approach should the developer use to scale the application efficiently?

Accepted Answer

Store connection IDs in Amazon DynamoDB and use the API Gateway Management API to send messages to all connections.. DynamoDB provides a scalable, serverless key-value store to persist WebSocket connection IDs, and the API Gateway Management API allows Lambda to send messages directly to any connected client via its connection ID. This combination efficiently handles the broadcast requirement without managing infrastructure, as Lambda can iterate over stored connection IDs and call the Management API for each message.

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Use Amazon ElastiCache to cache connection IDs and have Lambda send messages using the Redis pub/sub feature.

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Use Amazon SNS to publish messages to all connected clients via the WebSocket API.

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Use Amazon SQS to queue messages and have Lambda poll the queue to send messages to all connections.

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. Amazon Kinesis Data Streams is designed for real-time ingestion and buffering of large-scale streaming data, such as JSON messages from thousands of devices. It can capture and store data in shards for up to 365 days, allowing downstream consumers (e.g., Lambda, Kinesis Data Analytics) to process the data before storing it in Amazon S3. This makes it the correct choice for ingesting and buffering the streaming data before persistent storage.

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Amazon S3

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AWS Lambda

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Amazon Simple Queue Service (SQS)

Question 9

A developer is deploying a Docker container to Amazon ECS using the Fargate launch type. The developer wants to ensure the container has access to an Amazon RDS database. What is the best way to securely pass the database credentials to the container?

Accepted Answer

Use AWS Systems Manager Parameter Store or AWS Secrets Manager to store the credentials and reference them in the task definition.. AWS Systems Manager Parameter Store and AWS Secrets Manager are designed to securely store and manage sensitive information like database credentials. In Amazon ECS with Fargate, you can reference these secrets directly in the task definition using the 'secrets' parameter, which injects them as environment variables at runtime without exposing them in plain text or requiring additional code to fetch them. This approach adheres to the principle of least privilege and integrates natively with IAM roles for secure access.

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Pass the credentials as plain text environment variables in the task definition.

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Store the credentials in an Amazon S3 bucket and download them at container startup.

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Store the credentials in the container image as environment variables.

Question 10

A developer must locally test a SAM-based Lambda function with an API event before deployment. Which tool command family is designed for this?

Accepted Answer

AWS SAM CLI local invoke/start-api. The AWS SAM CLI provides the `local invoke` and `local start-api` commands specifically for testing Lambda functions locally with simulated API Gateway events before deployment. `sam local start-api` creates a local HTTP server that mimics API Gateway, allowing developers to send requests to their Lambda functions as if they were deployed, while `sam local invoke` directly invokes the function with a specified event payload. This is the only tool family designed for local testing of SAM-based Lambda functions with API events.

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AWS Shield Advanced CLI

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AWS Organizations policy simulator

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Amazon Inspector SBOM export

Question 11

Messages in an SQS queue are processed successfully but later reappear and are processed again. What is the most likely configuration issue?

Accepted Answer

The visibility timeout is shorter than the processing time or messages are not deleted after processing. When a message is processed but not deleted from the SQS queue, or when the visibility timeout expires before processing completes, the message becomes visible again in the queue and can be consumed by another worker. This causes duplicate processing. The correct fix is to ensure the visibility timeout is set longer than the expected processing time and that the message is explicitly deleted after successful processing.

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The queue uses long polling

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The queue has a dead-letter queue

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The messages are encrypted with SSE-SQS

Question 12

A development team wants to automatically deploy a web application to Amazon EC2 instances when new code is pushed to the master branch of an AWS CodeCommit repository. Which AWS service should the team use to orchestrate the build, test, and deployment phases?

Accepted Answer

AWS CodePipeline. AWS CodePipeline is the correct service because it is a fully managed continuous delivery service that orchestrates the entire build, test, and deployment phases as a pipeline. It can be configured to automatically trigger on code pushes to the master branch of an AWS CodeCommit repository, then invoke AWS CodeBuild for building and testing, and finally deploy to EC2 instances via AWS CodeDeploy, providing end-to-end automation.

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AWS CloudFormation

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AWS CodeBuild

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AWS CodeDeploy

Question 13

A developer creates an AWS CloudFormation stack with the template snippet shown. The stack creation fails with the error: "Bucket with name my-unique-bucket-12345 already exists." What is the MOST likely cause?

Accepted Answer

The bucket name is already taken by another AWS account.. The error message 'Bucket with name my-unique-bucket-12345 already exists' indicates that the bucket name is globally unique across all AWS accounts. Since the bucket name is already taken, the most likely cause is that another AWS account has already created a bucket with that exact name. S3 bucket names are unique across all of AWS, not just within a single account or region.

Answer

The developer does not have permission to create S3 buckets.

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The CloudFormation template has a syntax error.

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The bucket name was used by another stack in the same account.

Question 14

A developer is troubleshooting an AWS Lambda function that experiences high latency for the first few invocations after being idle. The function is written in Python and uses a large library (e.g., Pandas). The function connects to an RDS database in a VPC. What is the most effective way to reduce the latency for the first invocation after idle?

Accepted Answer

Enable provisioned concurrency on the function.. Provisioned concurrency keeps a specified number of execution environments initialized and ready to respond immediately, eliminating the cold start latency that occurs after a period of idle time. This is the most direct solution for reducing latency on the first invocation after idle, especially for functions with large libraries like Pandas that take significant time to load.

Answer

Increase the function's memory allocation to 3008 MB.

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Move the large library to a Lambda layer.

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Replace the RDS database with Amazon DynamoDB.

Question 15

A developer is building a serverless application using AWS Lambda. The Lambda function needs to access a VPC to connect to an RDS database. Which TWO resources must the developer configure to allow the Lambda function to access the VPC?

Accepted Answer

A security group that allows inbound/outbound traffic to the RDS database.. A security group acts as a virtual firewall for the Lambda function, controlling inbound and outbound traffic. To connect to an RDS database in a VPC, the Lambda function's security group must allow outbound traffic to the RDS database's security group on the database port (e.g., 3306 for MySQL), and the RDS security group must allow inbound traffic from the Lambda security group. This two-way rule ensures the Lambda function can establish a TCP connection to the database.

Answer

A NAT gateway in the VPC.

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An IAM role with permissions to access RDS.

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An internet gateway attached to the VPC.