DVA-C02 Development with AWS Services Practice Test 7 — 15 Questions

Question 1

A developer is designing a serverless application that processes user-uploaded images. The images are uploaded to an S3 bucket, which triggers a Lambda function to create a thumbnail and store metadata in DynamoDB. The thumbnail creation is CPU-intensive and can take up to 10 seconds. The developer wants to minimize costs and ensure that the thumbnail is created as soon as possible. Which approach should the developer choose?

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

Accepted Answer

Use S3 event notifications to directly invoke the Lambda function.. S3 event notifications directly invoke the Lambda function asynchronously, which is the simplest, fastest, and most cost-effective approach for this use case. The Lambda function's 15-minute timeout easily accommodates the 10-second thumbnail creation, and direct invocation eliminates the cost and latency of additional intermediate services like SQS or Step Functions, ensuring the thumbnail is processed as soon as the image is uploaded.

Answer

Use AWS Step Functions to orchestrate the Lambda function and DynamoDB update.

Answer

Use an ECS Fargate task to process the images, triggered by S3 events.

Answer

Use an SQS queue between S3 and Lambda to buffer requests.

Question 2

A developer is configuring an Amazon S3 bucket for static website hosting. The website includes JavaScript that makes AJAX calls to an API Gateway endpoint. Which TWO actions should the developer take to allow cross-origin requests?

Accepted Answer

Enable CORS on the API Gateway API.. The API Gateway API must have CORS enabled to accept cross-origin requests from the S3-hosted static website. When the JavaScript in the website makes AJAX calls to a different origin (the API Gateway endpoint), the browser enforces CORS by first sending a preflight OPTIONS request; enabling CORS on API Gateway configures the necessary Access-Control-Allow-Origin headers in the response, allowing the browser to proceed with the actual request.

Option D is incorrect because the S3 bucket policy controls access to the S3 bucket itself, not cross-origin requests to an API Gateway endpoint. The browser's CORS check is based on the response headers from the API Gateway, not the S3 bucket policy. Therefore, enabling CORS on the API Gateway is sufficient.

Answer

Use Amazon CloudFront to serve the website and set CORS headers.

Answer

Add a CORS configuration to the S3 bucket.

Answer

Configure the S3 bucket policy to allow cross-origin access.

Answer

Modify the Lambda function to include CORS headers in the response.

Question 3

A company uses AWS CloudFormation to deploy infrastructure. A developer needs to update a stack that includes an RDS DB instance. The update requires modifying the DB instance's DB engine version. Which THREE strategies can the developer use to minimize downtime during the update?

Accepted Answer

Update the stack directly by modifying the DB engine version property in the template.. To upgrade an RDS DB engine version with minimal downtime and maintain CloudFormation management:
1. **RDS Blue/Green Deployments (Option C)**: Creates a staging environment, applies the engine upgrade to the green environment, and switches over with minimal downtime (typically under a minute).
2. **Read Replica Promotion (Option E)**: A read replica can be created and upgraded to the new version. Once upgraded, it is promoted to a standalone primary instance, and the CloudFormation stack is updated to point to this new instance, minimizing downtime.
3. **Direct Template Update (Option B)**: Modifying the `EngineVersion` property in the CloudFormation template directly performs an in-place upgrade. While this causes some downtime during the upgrade process, it is a standard strategy that avoids resource replacement and maintains stack consistency.

Option A is incorrect because performing the upgrade out-of-band via the CLI introduces drift and offers no downtime advantage over Option B. Option D is incorrect because deleting and recreating the stack causes complete data loss and maximum downtime.

Answer

Use the RDS modify-db-instance command to upgrade the engine version in-place.

Answer

Delete the current stack and create a new stack with the new engine version.

Question 4

A developer needs to store application configuration data (key-value pairs) that can be accessed by multiple microservices running on EC2 instances. The configuration data changes infrequently but must be retrievable with low latency. Which AWS service should the developer use?

Accepted Answer

AWS Systems Manager Parameter Store. AWS Systems Manager Parameter Store is designed specifically to store configuration data (such as database strings, license codes, or general key-value pairs) and secrets. It provides a centralized, secure, and hierarchical store that can be easily accessed by EC2 instances and microservices with low latency. Standard parameters are free of charge, making it the ideal choice for infrequently changing configuration data.

Answer

AWS AppConfig

Answer

Amazon S3

Answer

Amazon DynamoDB

Question 5

A developer is deploying an application using AWS CodeDeploy with an in-place deployment configuration. The application runs on an EC2 instance behind an Application Load Balancer. The deployment fails because the health check fails after the new version is installed. What should the developer do to prevent the deployment from failing due to health checks?

Accepted Answer

Configure a longer health check grace period in the CodeDeploy application specification.. Configuring a longer health check grace period in the CodeDeploy application specification allows the application to start and stabilize before the load balancer checks its health, preventing premature failure. Option A is incorrect because deregistering and re-registering the instance is manual and not a built-in CodeDeploy feature; it also disrupts traffic. Option B is wrong because blue/green deployment is a different strategy, but the question asks about in-place deployment. Option D is incorrect because increasing the health check interval does not provide a grace period; it only makes checks less frequent, which may still fail if the app takes time to start.

Answer

Deregister the instance from the target group before deployment and register it after.

Answer

Switch to a blue/green deployment strategy.

Answer

Increase the health check interval on the load balancer.

Question 6

A developer is building a REST API using Amazon API Gateway and AWS Lambda. The API should allow users to retrieve data from an Amazon DynamoDB table. The developer wants to minimize latency for frequently accessed data. What should the developer do?

Accepted Answer

Enable API Gateway caching.. To minimize latency for frequently accessed data in a REST API built with API Gateway and Lambda, enabling API Gateway caching is the most effective solution. When caching is enabled, API Gateway caches the responses from the integration (Lambda) for a specified Time-to-Live (TTL) period. For subsequent requests, API Gateway serves the response directly from the cache without invoking the Lambda function or querying DynamoDB, significantly reducing latency and backend load.

Answer

Deploy a CloudFront distribution in front of the API Gateway.

Answer

Increase the Lambda function memory to improve performance.

Answer

Use DynamoDB Accelerator (DAX) as a caching layer.

Question 7

A company has a web application running on Amazon ECS with Fargate launch type. The application needs to store and retrieve user session data. The sessions are small and require very low latency access. The development team wants a fully managed solution. Which storage options meet these requirements? (Choose TWO.)

Accepted Answer

Amazon DynamoDB. Amazon DynamoDB is correct because it is a fully managed NoSQL key-value database that provides single-digit millisecond latency for read and write operations, making it ideal for storing small session data with low latency requirements. It scales automatically and requires no server management, aligning with the fully managed requirement and the Fargate launch type's serverless nature.

Answer

Amazon S3

Answer

Amazon EFS

Answer

Amazon RDS for PostgreSQL

Question 8

A developer is deploying a serverless application using the AWS Serverless Application Model (SAM). The application consists of an API Gateway, Lambda functions, and a DynamoDB table. The developer wants to define and deploy this infrastructure as code. Which files and tools are required? (Choose THREE.)

Accepted Answer

aws cloudformation deploy command. The AWS SAM template file (template.yaml) is required to define the serverless application resources. The `aws cloudformation package` command uploads local artifacts (such as Lambda deployment packages) to an S3 bucket and returns a copy of the template with references to the S3 object locations. The `aws cloudformation deploy` command then provisions the stack using the processed template. Together, these three are essential for deploying a SAM application using CloudFormation commands. While SAM CLI provides convenient wrappers like `sam package` and `sam deploy`, the underlying CloudFormation commands can also be used directly.

Answer

Terraform configuration files

Answer

AWS CLI with aws lambda update-function-code command

Question 9

A developer is troubleshooting an issue where an IAM user is unable to upload a file to an S3 bucket that uses server-side encryption with AWS KMS (SSE-KMS). The IAM policy shown in the exhibit is attached to the user. What is the likely cause of the failure?

Accepted Answer

The user does not have kms:Encrypt permission on the KMS key.. To make this question usable, either an exhibit (image or code block of the IAM policy) must be provided, or the stem must be rewritten to describe the policy directly (e.g., 'The IAM user has an IAM policy that grants s3:PutObject on the bucket, but no KMS permissions are defined...').

Answer

The KMS key ARN in the resource statement is incorrect.

Answer

The user does not have s3:PutObject permission on the bucket.

Answer

The user does not have access to the KMS key at all.

Question 10

A developer is setting up an S3 bucket to trigger an AWS Lambda function when a new object is created. After configuring the event notification, the Lambda function is not invoked. The developer checks the Lambda resource-based policy, which is shown in the exhibit. What is the issue?

Accepted Answer

The policy is missing a condition that specifies the S3 bucket ARN.. First, the question is missing the exhibit showing the Lambda resource-based policy. Second, from a technical standpoint, if a Lambda resource-based policy grants 's3.amazonaws.com' the 'lambda:InvokeFunction' permission without a condition restricting it to a specific bucket ARN, the invocation will still succeed. AWS does not block the invocation; it merely flags it as a security risk (confused deputy). Therefore, the premise that the Lambda function is not invoked because of a missing condition is technically incorrect.

Answer

The Action is incorrect; it should be 'lambda:Invoke' instead of 'lambda:InvokeFunction'.

Answer

The principal is incorrect; it should be the S3 bucket ARN.

Answer

The policy is missing the 'Version' field.

Question 11

A company is using AWS Lambda functions to process events from Amazon S3. The functions are writing logs to CloudWatch Logs. Recently, they noticed that some logs are missing and the functions are experiencing throttling errors. What is the MOST likely cause?

Accepted Answer

The Lambda function's reserved concurrency is set to a low value.. The most likely cause of throttling errors is that the Lambda function's reserved concurrency is set too low. When a Lambda function's reserved concurrency limit is reached, additional invocation requests are throttled, resulting in missing logs. Option A is incorrect because log group retention affects log storage, not Lambda throttling. Option C is incorrect because IAM permissions affect the ability to write logs, not throttling. Option D is incorrect because while S3 can send many events, Lambda's concurrency limit is the direct cause of throttling.

Answer

The CloudWatch Logs log group retention policy is set too low.

Answer

The Lambda function's IAM role lacks permissions to write to CloudWatch Logs.

Answer

The S3 bucket is sending too many event notifications.

Question 12

A company has an AWS Lambda function that processes messages from an Amazon SQS queue. The function is triggered by the SQS queue. Recently, the function started failing due to timeout errors when processing large messages. The function's timeout is set to the maximum of 15 minutes. What should a developer do to resolve this issue?

Accepted Answer

Decrease the SQS batch size in the Lambda trigger.. When a Lambda function triggered by SQS times out and its timeout is already set to the maximum of 15 minutes, the standard solution is to decrease the batch size (BatchSize) in the event source mapping (Lambda trigger). This reduces the number of messages processed in a single invocation, thereby reducing the execution time per invocation and preventing timeouts. Splitting messages (Option D) is unnecessary and impractical since SQS messages are already limited to 256 KB.

Answer

Increase the SQS queue's visibility timeout.

Answer

Increase the maximum message size in the SQS queue.

Answer

Split the large messages into smaller messages before sending to SQS.

Question 13

A developer is using AWS X-Ray to trace requests through a microservices application. The application consists of several AWS Lambda functions that call each other and Amazon DynamoDB. The developer notices that some traces are incomplete and missing segments for downstream calls. What is the MOST likely cause?

Accepted Answer

The Lambda functions do not have the X-Ray SDK imported.. The Lambda functions need to import the X-Ray SDK to create subsegments for downstream calls and propagate the trace header. Without the SDK, traces will be missing segments for DynamoDB calls. DynamoDB does not have a per-table X-Ray tracing setting; tracing is achieved by instrumenting the client in the calling code.

Answer

The downstream DynamoDB table does not have X-Ray tracing enabled.

Answer

The X-Ray daemon is not running on the Lambda execution environment.

Answer

The X-Ray sampling rate is set too low.

Question 14

A company is running a web application on Amazon EC2 instances behind an Application Load Balancer (ALB). The application uses Amazon ElastiCache for session state. Recently, users are experiencing intermittent session timeouts and slow page loads. The developer suspects the issue is related to the ElastiCache cluster. Which THREE actions should the developer take to troubleshoot and resolve the issue? (Choose THREE.)

Accepted Answer

Monitor the ElastiCache cluster's CPU utilization and cache hit ratio in CloudWatch.. Monitoring CPU utilization and cache hit ratio in CloudWatch helps identify whether the ElastiCache cluster is under-provisioned or experiencing inefficient caching. High CPU utilization indicates the node is overloaded, while a low cache hit ratio suggests that the application is frequently missing the cache and falling back to the database, causing slow page loads and session timeouts.

Answer

Enable Encryption in transit for the ElastiCache cluster.

Answer

Enable Multi-AZ replication for the ElastiCache cluster.

Question 15

A developer is using AWS Lambda to process files uploaded to an S3 bucket. The Lambda function is triggered by S3 events. The developer notices that the function sometimes processes the same file multiple times. Which TWO steps should the developer take to make the processing idempotent? (Choose TWO.)

Accepted Answer

Check if the file has already been processed by storing a marker in DynamoDB.. Storing a marker in DynamoDB (e.g., a record with the S3 object key as the partition key) allows the Lambda function to check if a file has already been processed before performing the work. This ensures that even if the same S3 event is delivered multiple times (due to retries or duplicate notifications), the function will skip reprocessing, making the operation idempotent.

Answer

Reduce the S3 event batch size in the Lambda trigger.

Answer

Increase the Lambda function's timeout.

Answer

Enable S3 versioning on the bucket.