DVA-C02 Development with AWS Services Practice Test 27 — 15 Questions

Question 1

A developer is using Amazon DynamoDB as the data store for a web application. The application experiences frequent throttling errors. Which action can reduce throttling without changing the application code?

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

Accepted Answer

Enable DynamoDB Auto Scaling. DynamoDB Auto Scaling automatically adjusts the provisioned throughput capacity based on actual traffic patterns, using the AWS Application Auto Scaling service. This prevents throttling by increasing capacity during demand spikes and reduces costs by scaling down during low traffic, all without requiring any code changes.

Answer

Add a secondary index

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Decrease the provisioned write capacity

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Increase the provisioned read capacity only

Question 2

A company has a Lambda function that processes records from an SQS queue. The function is failing intermittently with timeout errors. The processing time per record varies, but the SQS queue has a visibility timeout of 30 seconds. The Lambda function has a timeout of 1 minute. What is the MOST likely cause of the timeout errors?

Accepted Answer

The SQS visibility timeout is shorter than the Lambda function timeout.. When the SQS visibility timeout (30 seconds) is shorter than the Lambda function timeout (1 minute), the message becomes visible again in the queue before the function finishes processing it. This causes the same message to be picked up by another consumer (or the same Lambda invocation) while the original invocation is still running, leading to duplicate processing and eventual timeout errors as the function repeatedly attempts to process the same record.

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

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The SQS queue has too many messages causing Lambda to throttle.

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The SQS queue's default visibility timeout of 30 seconds is too long.

Question 3

A developer is building a serverless application using AWS Lambda and Amazon DynamoDB. The Lambda function needs to read and write items to a DynamoDB table. What is the BEST way to securely provide the Lambda function with the necessary AWS credentials?

Accepted Answer

Create an IAM role with DynamoDB permissions and attach it to the Lambda function.. The best practice for granting AWS Lambda functions access to DynamoDB is to create an IAM role with the necessary DynamoDB permissions (e.g., dynamodb:GetItem, dynamodb:PutItem) and attach that role to the Lambda function. This follows the principle of least privilege and leverages AWS Identity and Access Management (IAM) roles, which provide temporary, automatically rotated credentials via the AWS Security Token Service (STS). This approach eliminates the need to manage long-term access keys and ensures secure, auditable access.

Answer

Store the AWS access key and secret key in the Lambda environment variables.

Answer

Create an IAM user with programmatic access and store the credentials in the Lambda code.

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Use the Lambda function's default full admin access provided by AWS.

Question 4

A company is using AWS CodeDeploy to deploy an application to an Auto Scaling group. The deployment fails with the error 'The overall deployment failed because too many individual instances failed to deploy.' The CodeDeploy agent logs show that the BeforeInstall lifecycle event script returned a non-zero exit code. What is the MOST likely cause of this issue?

Accepted Answer

The BeforeInstall script has a bug that causes it to exit with a non-zero status.. The error message explicitly states that the CodeDeploy agent logs show the BeforeInstall lifecycle event script returned a non-zero exit code. This directly indicates that the script itself failed during execution, which is the most likely cause of the deployment failure. The BeforeInstall script is a custom script run by the CodeDeploy agent on each instance, and a non-zero exit code signals an error condition that halts the deployment for that instance.

Answer

The application revision is missing from the S3 bucket.

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The IAM instance profile does not have permissions to call CodeDeploy APIs.

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The CodeDeploy agent is not running on the instances.

Question 5

A developer is writing a Lambda function that processes events from an Amazon S3 bucket. The function needs to access a DynamoDB table to store metadata about the S3 objects. Which of the following is the MOST efficient way to initialize the DynamoDB client in the Lambda function?

Accepted Answer

Create the DynamoDB client outside the Lambda handler function, in the global scope.. Initializing the DynamoDB client outside the Lambda handler (in global scope) allows the client to be reused across multiple invocations within the same execution environment. This avoids the overhead of creating a new client on every invocation, which reduces latency and conserves resources. AWS Lambda reuses the global scope for subsequent invocations after the first, making this the most efficient approach.

Answer

Store the DynamoDB table name as a global variable and create the client inside the handler.

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Use a static variable inside the handler to cache the DynamoDB client.

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Create the DynamoDB client inside the Lambda handler function every invocation.

Question 6

A developer needs to store application configuration data, such as database connection strings and API keys, for a microservices application running on Amazon ECS. The configuration must be encrypted at rest and easily auditable. Which AWS service should the developer use?

Accepted Answer

AWS Systems Manager Parameter Store.. AWS Systems Manager Parameter Store is the correct choice because it is designed to store application configuration data like database connection strings and API keys, integrates natively with Amazon ECS for secure parameter retrieval, and supports encryption at rest using AWS KMS. It also provides built-in auditing through AWS CloudTrail, which logs all API calls to the Parameter Store, meeting the auditability requirement.

Answer

AWS Secrets Manager.

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Amazon S3 with server-side encryption.

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Amazon DynamoDB with encryption at rest.

Question 7

A company runs a stateful web application on EC2 instances behind an Application Load Balancer. The application uses WebSockets for real-time communication. The company wants to use AWS CodeDeploy to deploy updates with minimal downtime. Which deployment configuration should the developer use?

Accepted Answer

Blue/green deployment.. Blue/green deployment is correct because it allows the company to deploy a new version of the application on a separate set of EC2 instances (green environment) while the current version continues to serve traffic on the original set (blue environment). Once the green environment is fully tested and healthy, the Application Load Balancer can instantly switch traffic to it, minimizing downtime. This approach is ideal for stateful WebSocket applications because it avoids terminating active connections during the deployment, as the blue environment remains operational until the switch is complete.

Answer

Canary deployment.

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In-place deployment.

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Immutable deployment.

Question 8

A developer is using Amazon API Gateway to expose a Lambda function as a REST API. The Lambda function queries an Amazon RDS database. Under heavy load, the database connection pool is exhausted, causing errors. What is the BEST way to manage database connections in this serverless architecture?

Accepted Answer

Use Amazon RDS Proxy to pool and share database connections.. Amazon RDS Proxy sits between Lambda and RDS, managing a pool of database connections that can be reused across multiple concurrent Lambda invocations. This prevents connection exhaustion under heavy load without requiring code changes, as the proxy handles connection multiplexing and keeps idle connections warm.

Answer

Migrate the database to Amazon DynamoDB.

Answer

Increase the concurrency limit of the Lambda function.

Answer

Use Amazon ElastiCache to cache database connections.

Question 9

A developer is building a CI/CD pipeline using AWS CodePipeline. The source stage is an Amazon S3 bucket. The developer wants to automatically start the pipeline when a new file is uploaded to the S3 bucket. What should the developer do?

Accepted Answer

Create an Amazon CloudWatch Events rule that triggers on S3 object creation events and targets the pipeline.. Amazon CloudWatch Events (now Amazon EventBridge) can directly target an AWS CodePipeline pipeline as a rule target. By creating a rule that matches S3 object creation events (e.g., `s3:ObjectCreated:*`), the pipeline is automatically triggered without any intermediate polling, custom code, or additional services. This is the native, serverless integration recommended by AWS.

Answer

Configure the S3 bucket to send events to an SQS queue, and poll the queue from CodePipeline.

Answer

Set up a periodic Lambda function that checks the S3 bucket for new files and starts the pipeline.

Answer

Configure the S3 bucket to send events to an SNS topic, and subscribe CodePipeline to the topic.

Question 10

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.

Answer

An IAM role with permissions to access RDS.

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An internet gateway attached to the VPC.

Question 11

A developer is building a serverless application using AWS Lambda to process images uploaded to an S3 bucket. The Lambda function needs to resize the image and store the result in another S3 bucket. The developer notices that the Lambda function fails intermittently with timeout errors for large images. What is the MOST efficient solution to resolve this issue?

Accepted Answer

Increase the Lambda function timeout and memory allocation to accommodate larger images.. Increasing the Lambda function timeout and memory allocation directly addresses the root cause of the failure: large images require more processing time and memory. Lambda's CPU and I/O throughput scale proportionally with allocated memory, so raising both parameters provides the necessary resources to complete the resize operation within the function's execution environment.

Answer

Limit the S3 event notification to only trigger for images smaller than 5 MB.

Answer

Refactor the Lambda function to use multi-threading for parallel processing of image chunks.

Answer

Use AWS Step Functions to orchestrate the image processing in smaller steps.

Question 12

A company runs a containerized application on Amazon ECS using Fargate launch type. The application needs to read and write files to a shared file system across multiple tasks. The development team wants a solution that provides high throughput and is POSIX-compliant. Which storage solution should the team use?

Accepted Answer

Amazon EFS. Amazon EFS is the correct choice because it provides a fully managed, POSIX-compliant shared file system that can be mounted concurrently by multiple Amazon ECS tasks using the Fargate launch type. EFS uses the NFSv4.1 protocol, supports high throughput (up to 10 GB/s with Bursting or Provisioned Throughput modes), and automatically scales storage capacity as files are added or removed, making it ideal for shared read/write workloads across containers.

Answer

Amazon S3 with mountpoint-s3

Answer

Amazon EBS with multi-attach enabled

Answer

Amazon FSx for Windows File Server

Question 13

A company is using AWS Lambda to process messages from an Amazon SQS queue. The Lambda function is configured with a reserved concurrency of 10. The SQS queue receives a burst of 1000 messages. The Lambda function processes each message in about 5 seconds. What is the most likely behavior of the system?

Accepted Answer

Lambda processes up to 10 messages concurrently, and the rest remain in the queue until processing capacity is available.. Lambda's reserved concurrency of 10 caps the maximum number of concurrent executions. When the SQS queue receives 1000 messages, Lambda polls the queue and invokes the function with up to 10 messages at a time (based on batch size, default 1). The remaining messages stay in the queue and are retried after the visibility timeout expires, as Lambda processes messages in batches limited by the reserved concurrency.

Answer

Lambda rejects the messages and sends them to the dead-letter queue.

Answer

Lambda automatically scales up to 1000 concurrent executions to process all messages quickly.

Answer

Lambda increases the reserved concurrency to accommodate the burst.

Question 14

A company is running a monolithic application on an EC2 instance. The application currently stores session state in local memory on the instance. The company plans to scale the application horizontally by adding more instances behind a load balancer. What change is required to ensure that session state is preserved across requests?

Accepted Answer

Use Amazon ElastiCache to store session state externally.. Amazon ElastiCache provides a managed, in-memory caching service (e.g., Redis or Memcached) that can store session state externally. By moving session data out of the EC2 instance's local memory and into a shared, low-latency data store, all instances behind the load balancer can access the same session state, ensuring persistence across requests regardless of which instance handles the request.

Answer

Store session data in Amazon S3 and retrieve it on each request.

Answer

Increase the EC2 instance size to handle more sessions per instance.

Answer

Use an Amazon RDS database to store session state.

Question 15

A developer is creating an AWS Lambda function that processes events from an Amazon S3 bucket. The function writes logs to Amazon CloudWatch Logs. The developer wants to ensure that the Lambda function has the minimum required permissions. Which IAM policy should be attached to the Lambda execution role?

Accepted Answer

A policy that includes 'logs:CreateLogGroup', 'logs:CreateLogStream', 'logs:PutLogEvents', and 's3:GetObject' on the specific bucket.. It grants the minimum required permissions for the Lambda function to read objects from the specific S3 bucket (s3:GetObject) and to write logs to CloudWatch Logs (logs:CreateLogGroup, logs:CreateLogStream, logs:PutLogEvents). The s3:GetObject action is necessary to process events from S3, and the three logs actions are the minimum needed for the Lambda runtime to create a log group, create a log stream, and write log events. This policy follows the principle of least privilege by scoping permissions to the specific bucket and avoiding wildcards.

Answer

A policy that includes 'logs:CreateLogStream', 'logs:PutLogEvents', and 's3:*' on the bucket.

Answer

A policy that includes 'logs:*' and 's3:*' on the bucket.

Answer

A policy that includes 'logs:PutLogEvents' and 's3:ListBucket' on the bucket.