DVA-C02 Mock Exam 71 — 25 Questions

Question 1

Match each AWS security feature to its function.

Question 2

A developer has an AWS Lambda function that processes messages from an Amazon SQS queue. The function is configured with a batch size of 10, reserved concurrency of 5, and a timeout of 5 minutes. The SQS queue has a large backlog, and CloudWatch metrics show high throttling (Throttles) for the Lambda function. The function is idempotent and can process up to 100 messages in a single invocation. What is the MOST effective way to increase throughput without increasing the reserved concurrency?

Accepted Answer

Increase the batch size to 100.. Increasing the batch size to 100 allows each Lambda invocation to process up to 100 messages from the SQS queue instead of the current 10. Since the function is idempotent and can handle 100 messages per invocation, this change maximizes the number of messages processed per invocation without altering the reserved concurrency of 5. With a batch size of 100, each of the 5 concurrent invocations can process up to 100 messages, yielding a potential throughput of 500 messages per invocation cycle, which directly reduces the backlog and throttling by consuming messages faster.

Answer

Increase the reserved concurrency to 10.

Answer

Reduce the batch size to 1.

Answer

Enable the SQS queue to use long polling.

Question 3

A developer is building a REST API using Amazon API Gateway and wants to validate the incoming request body against a JSON schema before passing the request to the backend Lambda function. Which API Gateway feature should the developer use?

Accepted Answer

Request validation. API Gateway's request validation feature allows you to define a JSON schema (using JSON Schema Draft 4) for the request body and automatically reject requests that do not conform before they reach the backend. This offloads validation from the Lambda function, reducing cold start overhead and ensuring only valid payloads are processed. The developer can configure this in the API Gateway console or via the OpenAPI specification.

Answer

Mapping templates

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Integration request

Answer

Stage variables

Question 4

A developer is building a serverless API using Amazon API Gateway and AWS Lambda. The API accepts JSON payloads in the request body. The developer wants to ensure that incoming requests have a valid structure before being passed to the Lambda function to reduce unnecessary invocations. Which API Gateway feature should the developer use?

Accepted Answer

Request validation using models and request validators. Option A is correct because API Gateway's request validation feature allows you to define a JSON Schema model for the request body and attach a request validator to the method. This validates the payload structure before the request reaches the Lambda function, preventing invalid payloads from triggering unnecessary invocations and reducing costs.

Answer

Usage plans with API keys

Answer

WAF (AWS WAF) integration

Answer

Custom authorizer (Lambda authorizer)

Question 5

A developer is building a RESTful API using AWS Lambda and Amazon API Gateway. The API needs to support HTTP methods GET, POST, and DELETE. The developer wants to minimize code and operational overhead. Which API Gateway integration type should the developer use?

Accepted Answer

Lambda proxy integration. Lambda proxy integration is the simplest and most common approach. It passes the entire request to the Lambda function, which handles routing and response formatting, minimizing code and overhead. Custom integration requires mapping templates, HTTP integration forwards to an HTTP endpoint, and mock integration is for testing.

Answer

Lambda custom integration

Answer

HTTP integration

Answer

Mock integration

Question 6

A developer is building a serverless application using AWS Lambda and Amazon API Gateway. The API must support different HTTP methods (GET, POST, PUT, DELETE) for the same resource path. The developer wants to define the API in a single Lambda function that can handle all methods without additional mapping configuration. Which Lambda integration type should the developer use?

Accepted Answer

Lambda proxy integration. Lambda proxy integration (option A) is correct because it allows a single Lambda function to handle all HTTP methods (GET, POST, PUT, DELETE) for the same resource path without additional mapping configuration. In this integration type, API Gateway passes the entire client request (method, headers, query parameters, body) as a JSON event to the Lambda function, and the function must return a response in a specific format that includes status code, headers, and body. This eliminates the need for manual mapping templates or method-specific configurations.

Answer

Lambda custom integration

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AWS service integration

Answer

HTTP integration

Question 7

A developer is creating an AWS Lambda function that needs to access files from an Amazon EFS file system. The Lambda function must be configured to access the VPC. Which of the following is required to allow the Lambda function to mount the EFS file system?

Accepted Answer

The Lambda function must have the AWSLambdaVPCAccessExecutionRole managed policy attached.. The AWSLambdaVPCAccessExecutionRole managed policy provides the necessary permissions for Lambda to manage elastic network interfaces (ENIs) in a VPC, which is required for Lambda to connect to an EFS file system via mount targets. Without this policy, the Lambda function cannot create or manage the ENI needed to route traffic to the EFS mount target within the VPC.

Answer

The Lambda function must be in the same Availability Zone as the EFS mount target.

Answer

The Lambda function must have the AmazonElasticFileSystemClientReadWriteAccess managed policy attached.

Answer

The Lambda function must have the efs:MountFileSystem permission in its execution role.

Question 8

A developer is creating a REST API using Amazon API Gateway and multiple AWS Lambda functions for different endpoints. The API must support CORS for a web application hosted on a different domain. The developer is using Lambda proxy integration. Which configuration is required to enable CORS?

Accepted Answer

Enable CORS in API Gateway and configure the Lambda functions to return the required CORS headers.. With Lambda proxy integration in API Gateway, the entire request and response are passed through to the Lambda function, which must return the HTTP response including status code, headers, and body. To enable CORS, the Lambda function must include the required CORS headers (e.g., Access-Control-Allow-Origin) in its response. While API Gateway can be configured to add CORS headers for non-proxy integrations, with proxy integration the Lambda function is solely responsible for returning all headers.

Answer

Configure API Gateway to return CORS headers and Lambda functions can ignore CORS.

Answer

Configure Lambda functions to return CORS headers and API Gateway will pass them through automatically.

Answer

Use a Lambda@Edge function at Amazon CloudFront to add CORS headers.

Question 9

A developer configures an AWS Lambda function to process image files uploaded to an S3 bucket. The bucket receives a mix of .jpg, .png, and .pdf files. The developer wants to invoke the Lambda function only for image files to reduce costs. Which configuration should the developer use?

Accepted Answer

Configure an S3 event notification with a suffix filter '.jpg' and '.png'. Option B is correct because S3 event notifications support suffix filtering, allowing you to specify object key suffixes like '.jpg' and '.png'. This ensures the Lambda function is invoked only when objects with those extensions are uploaded, filtering out .pdf files and reducing unnecessary invocations and costs.

Answer

Configure an S3 event notification with a prefix filter 'images/'

Answer

Create a Lambda resource-based policy that denies invocation from S3 for .pdf objects

Answer

Add an S3 bucket policy that denies PutObject for any object that is not a .jpg or .png

Question 10

A developer is running a web application on multiple Amazon EC2 instances behind an Application Load Balancer (ALB). The application needs to store user session state that must be available across all instances. The session data is small and temporary but must survive individual instance failures. Which AWS service should the developer use to store this session state?

Accepted Answer

Store session state in an Amazon ElastiCache cluster. Amazon ElastiCache (e.g., using Redis or Memcached) provides a centralized, in-memory data store that is external to the EC2 instances. This allows all instances behind the ALB to read and write the same session state, ensuring consistency across the fleet. Because the data is stored in a managed cluster, it survives individual instance failures and is ideal for small, temporary session data that requires low-latency access.

Answer

Store session state in the /tmp directory of each EC2 instance

Answer

Use an Amazon SQS queue to persist session data

Answer

Store session state in an Amazon S3 bucket

Question 11

A developer is building a serverless application using AWS Step Functions to orchestrate multiple AWS Lambda functions. One of the Lambda functions occasionally fails due to a transient error. The developer wants the Step Functions execution to automatically retry the failed task up to three times with exponential backoff. Which configuration should the developer set in the Step Functions state machine definition?

Accepted Answer

Use the Amazon States Language (ASL) Retry field in the Task state definition.. Option B is correct because the Amazon States Language (ASL) provides a native Retry field within a Task state definition that allows you to specify retry policies, including a maximum retry count and exponential backoff. This is the intended mechanism for handling transient failures in Step Functions without requiring custom code or external retry logic.

Answer

Add a Retry clause in the Lambda function's configuration with a maximum retry count of 3.

Answer

Wrap the Lambda function invocation in a custom while loop within the function code.

Answer

Use the Amazon States Language Catch field in the Task state to redirect to a retry logic.

Question 12

A developer has an Amazon S3 bucket containing private user documents. The application must generate a time-limited URL for users to download their own documents without requiring the users to have AWS credentials. Which solution should the developer use?

Accepted Answer

Create a pre-signed URL for each object using the AWS SDK with an appropriate expiration time.. Pre-signed URLs allow temporary, time-limited access to private S3 objects without requiring the user to have AWS credentials. The developer generates the URL server-side using the AWS SDK, embedding an expiration time, and the user can download the object directly via HTTP GET. This meets the requirement of granting ephemeral access to specific documents for unauthenticated users.

Answer

Use CloudFront signed URLs with an origin access identity (OAI) to restrict access to the S3 bucket.

Answer

Set a bucket policy that allows public read access for the specific users based on their IP addresses.

Answer

Provide the users with IAM user credentials that have read access to the bucket.

Question 13

A developer is designing a REST API using Amazon API Gateway that experiences high traffic with many repeated requests for the same data. The developer wants to reduce backend load and improve response times. Which feature should the developer enable on the API Gateway method?

Accepted Answer

Enable API Gateway caching. API Gateway caching stores responses from backend endpoints for a configurable Time-to-Live (TTL). When a request for the same data arrives, API Gateway serves the cached response directly without invoking the backend, reducing load and improving latency. This is the most straightforward and managed solution for repeated requests at the API layer.

Answer

Implement caching in the Lambda function using a local cache

Answer

Use an Amazon ElastiCache Redis cluster and modify the Lambda function to check the cache first

Answer

Place an Amazon CloudFront distribution in front of API Gateway

Question 14

A developer is building a serverless web application using AWS Lambda and Amazon DynamoDB. The application needs to perform complex aggregations on data stored in DynamoDB. Which AWS service should the developer use to perform these aggregations efficiently without reading all the data into Lambda?

Accepted Answer

DynamoDB Streams with AWS Lambda. Option C is correct because DynamoDB Streams captures item-level changes in near real-time and can trigger a Lambda function to perform incremental aggregations without scanning the entire table. This pattern avoids reading all data into Lambda, making it efficient for continuous aggregation workloads.

Answer

AWS Glue

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Amazon EMR

Answer

Amazon Redshift

Question 15

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.

Answer

Amazon CloudFront as a custom domain.

Answer

Lambda@Edge for caching.

Answer

S3 Transfer Acceleration.

Question 16

A developer has an AWS Lambda function that processes messages from an Amazon SQS standard queue. The function is idempotent and currently has a batch size of 10. The developer wants to increase throughput and increases the batch size to 100. After the change, CloudWatch metrics show a significant increase in throttles and the queue backlog is growing. The function's reserved concurrency is set to 10. What is the most effective action to resolve the throttling and improve throughput?

Accepted Answer

Increase the reserved concurrency of the Lambda function. Increasing the reserved concurrency from 10 to a higher value directly addresses the root cause of throttling. With a batch size of 100, each invocation processes more messages, but the function's reserved concurrency of 10 limits the maximum number of concurrent executions to 10. This means the Lambda service can only invoke the function 10 times at once, regardless of how many messages are in the queue. By raising reserved concurrency, you allow more concurrent invocations to handle the larger batches, reducing throttling and improving throughput.

Answer

Increase the memory allocation of the Lambda function

Answer

Switch the SQS queue to a FIFO queue

Answer

Decrease the batch size back to 10

Question 17

A developer is building a RESTful API that allows clients to query a database and retrieve results. The backend logic is implemented in AWS Lambda, which queries an Amazon DynamoDB table. The developer wants to expose the API over HTTPS and manage authentication and throttling. Which AWS service should the developer use to create and manage the API endpoints?

Accepted Answer

Amazon API Gateway. Amazon API Gateway is the correct choice because it is a fully managed service that enables developers to create, publish, maintain, monitor, and secure RESTful APIs at any scale. It directly supports HTTPS endpoints, integrates natively with AWS Lambda for backend logic, and provides built-in features for authentication (e.g., IAM, Cognito, Lambda authorizers) and throttling (usage plans and rate limits). This makes it the ideal service for exposing a Lambda-backed DynamoDB query as a secure, managed API.

Answer

Application Load Balancer

Answer

AWS CloudFront

Answer

Amazon S3

Question 18

A developer is migrating a monolithic application to a microservices architecture on AWS. The application uses a relational database. The developer wants to use Amazon RDS for the database and needs to ensure that each microservice can only access its own set of tables. Which approach should the developer take?

Accepted Answer

Use RDS with IAM database authentication and create database users with limited privileges for each microservice.. Option B is correct because IAM database authentication allows the developer to create database users with granular, table-level privileges using standard SQL GRANT statements, ensuring each microservice can only access its own set of tables. By combining IAM roles with database user credentials, the developer can enforce least-privilege access without sharing a single database user across services. This approach directly addresses the requirement for per-microservice table isolation while leveraging RDS's native authentication and authorization capabilities.

Answer

Create a single RDS instance with a separate database per microservice.

Answer

Use RDS in a VPC and restrict network access per microservice using security groups.

Answer

Use Amazon RDS Proxy to control access.

Question 19

A developer is building a serverless application that uses Amazon S3 event notifications to trigger an AWS Lambda function for thumbnail generation. The developer wants to ensure that duplicate S3 events do not cause the same image to be processed multiple times. Which approach should the developer implement to ensure idempotent processing?

Accepted Answer

Store the object key and event ID in a DynamoDB table and check for duplicates before processing. Option A is correct because storing the S3 object key and event ID in a DynamoDB table with a TTL attribute allows the Lambda function to perform a conditional write (or check for an existing item) before processing. This ensures that even if duplicate S3 events are delivered (e.g., due to S3's at-least-once delivery guarantee), the same image is only processed once, achieving idempotency.

Answer

Set the Lambda function's concurrency to 1 to prevent concurrent executions

Answer

Use an Amazon SQS FIFO queue as the event destination

Answer

Enable S3 event notification filtering based on object size

Question 20

A developer is building a serverless application that uses an Amazon SQS FIFO queue to process orders. The orders must be processed exactly once and in the order they are received. The developer uses an AWS Lambda function as the consumer. Despite using a FIFO queue, the developer notices that some orders are being processed more than once. What is the most likely cause of this behavior?

Accepted Answer

The Lambda function is not deleting messages from the queue after successful processing, so they become visible again after the visibility timeout.. The most likely cause is that the Lambda function is not deleting messages from the SQS FIFO queue after successful processing. By default, Lambda does not automatically delete messages; it relies on the function code to call the `DeleteMessage` API. If the function fails to delete a message, it remains in the queue and becomes visible again after the visibility timeout expires, leading to duplicate processing even though the queue is FIFO.

Answer

The Lambda function is configured with a batch size greater than 1, causing multiple messages to be processed at once and some to be duplicated.

Answer

The SQS queue has a message retention period set too low, causing messages to be deleted automatically and re-queued.

Answer

The Lambda function's execution role does not have permission to delete messages from the queue.