DVA-C02 Development with AWS Services Practice Test 5 — 15 Questions

Question 1

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.

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Lambda custom integration

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HTTP integration

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Mock integration

Question 2

A developer is using AWS AppSync to build a GraphQL API. The API needs to allow clients to receive real-time updates when data changes in a DynamoDB table. Which AppSync feature should the developer use?

Accepted Answer

Subscriptions. Subscriptions in AWS AppSync are the feature designed for real-time updates. They use WebSocket connections to push data to clients automatically when a mutation modifies the underlying data source, such as a DynamoDB table. By configuring a subscription on a specific mutation, the developer enables clients to receive live changes without polling.

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Resolvers

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Queries

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Mutations

Question 3

A developer wants to store session state data for a web application running on multiple EC2 instances behind an Application Load Balancer. The data is ephemeral and should not persist if an instance is terminated. Which storage option should the developer use?

Accepted Answer

Amazon ElastiCache. Amazon ElastiCache is the correct choice because it provides an in-memory caching service (e.g., Redis or Memcached) that is ideal for storing ephemeral session state data. The data is stored in memory, not on disk, so it is automatically lost when an EC2 instance is terminated, matching the requirement that session data should not persist. Additionally, ElastiCache is designed for low-latency access, making it suitable for session state that must be quickly read and written by multiple instances behind an Application Load Balancer.

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Amazon RDS

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Amazon S3

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Amazon EFS

Question 4

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.

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The Lambda function must have the AmazonElasticFileSystemClientReadWriteAccess managed policy attached.

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

Question 5

A developer is building a serverless application using AWS Lambda that needs to connect to an Amazon RDS MySQL database. The function will be deployed in a VPC. Which resource should the developer use to ensure secure and efficient database connections?

Accepted Answer

RDS Proxy. RDS Proxy is the correct choice because it manages a pool of database connections, allowing Lambda functions to reuse them efficiently and avoid exhausting MySQL connection limits under high concurrency. It also enforces IAM authentication and securely stores credentials in AWS Secrets Manager, eliminating the need to hardcode database passwords in the function code.

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NAT Gateway

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VPC Endpoint

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AWS PrivateLink

Question 6

A developer is creating an API with Amazon API Gateway that needs to accept binary data (e.g., images) and store them directly in an S3 bucket. The developer wants to minimize backend complexity. Which integration type should be used?

Accepted Answer

AWS service integration with S3. AWS service integration with S3 allows API Gateway to directly proxy binary data (e.g., images) to an S3 bucket without invoking a Lambda function or other backend. This minimizes backend complexity because the API Gateway handles the request transformation and passes the payload directly to S3 via the PutObject API action, eliminating the need for custom code.

Answer

Lambda proxy integration

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HTTP integration

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Mock integration

Question 7

A developer is building a REST API using Amazon API Gateway and AWS Lambda. The API needs to support a custom domain name and an SSL/TLS certificate. Which AWS service should the developer use to manage the SSL/TLS certificate?

Accepted Answer

AWS Certificate Manager (ACM). AWS Certificate Manager (ACM) is the correct service for provisioning, managing, and deploying SSL/TLS certificates for use with AWS services like API Gateway. ACM integrates directly with API Gateway to automatically renew certificates and attach them to custom domain names, ensuring secure HTTPS connections without manual intervention.

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AWS Key Management Service (AWS KMS)

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AWS Identity and Access Management (IAM)

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AWS Secrets Manager

Question 8

A developer is building a microservice that needs to invoke another AWS Lambda function and wait for the result to continue processing. Which Lambda invocation type must the developer use to achieve synchronous invocation?

Accepted Answer

RequestResponse. The RequestResponse invocation type is the correct choice for synchronous invocation of a Lambda function, where the caller waits for the function to execute and receive a response. This is the default invocation type when using the Invoke API with InvocationType set to 'RequestResponse', and it is required for microservices that need to block until the downstream Lambda returns a result.

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Event

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DryRun

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None of the above

Question 9

A developer is writing a Lambda function that processes images uploaded to an S3 bucket. The function needs to extract metadata from the image. Which S3 feature can be used to automatically trigger the Lambda function?

Accepted Answer

S3 Events. Amazon S3 Events can be configured to send a notification when an object is created (e.g., via PutObject) in an S3 bucket. This event can directly invoke an AWS Lambda function, making it the correct service to automatically trigger the function upon image upload. The developer simply needs to set up an S3 event notification with the Lambda function as the destination.

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S3 Inventory

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S3 Transfer Acceleration

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S3 Batch Operations

Question 10

A developer is building a serverless application using AWS Lambda. The function needs to access an S3 bucket to read a configuration file. What is the best way to provide the Lambda function with the bucket name?

Accepted Answer

Store the bucket name in an environment variable for the Lambda function.. Option B is correct because AWS Lambda environment variables provide a secure, configurable, and decoupled way to pass the S3 bucket name to the function without hardcoding it in the code. This follows the principle of infrastructure as code and allows the same function code to be reused across different environments (e.g., dev, staging, prod) by simply changing the environment variable value. Environment variables are encrypted at rest by default using AWS KMS, ensuring the bucket name is not exposed in plaintext within the code repository.

Answer

Hardcode the bucket name in the Lambda function code.

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Read the bucket name from a text file stored in the same bucket.

Answer

Use a KMS key to encrypt the bucket name and decrypt it in the function.

Question 11

A developer is creating an AWS Lambda function to process events from an Amazon SQS queue. The function must process each message exactly once and in order. Which SQS queue type should the developer use?

Accepted Answer

FIFO queue.. The correct answer is B, FIFO queue. FIFO (First-In-First-Out) queues guarantee exactly-once processing and preserve the order of messages, which is required by the use case. Standard queues offer at-least-once delivery and do not guarantee order, making them unsuitable for this requirement.

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Standard queue.

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Dead-letter queue.

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Delay queue.

Question 12

A Lambda function processes messages from an SQS standard queue and writes results to DynamoDB. Duplicate writes occasionally occur after retries. Which two changes best make the processing idempotent?

Accepted Answer

Use a deterministic idempotency key stored with a conditional write in DynamoDB. Option A is correct because using a deterministic idempotency key (e.g., a business transaction ID) combined with a conditional write in DynamoDB ensures that if the same message is processed more than once, the second write attempt will fail because the item already exists. This prevents duplicate records even when Lambda retries after a failure or timeout, making the processing idempotent at the database level.

Answer

Increase the Lambda timeout to 15 minutes

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Disable SQS visibility timeout

Question 13

An API Gateway REST API invokes Lambda synchronously. Clients receive 502 responses after a deployment, but Lambda logs show a successful business operation. What is the most likely issue?

Accepted Answer

The Lambda proxy integration response format is invalid. Lambda proxy integration requires the response to be in a specific JSON format: `{"statusCode": ..., "headers": ..., "body": ...}`. If the Lambda function returns a plain string or an object missing these keys, API Gateway cannot map it to an HTTP response, resulting in a 502 Internal Server Error. The successful business operation in logs confirms the Lambda code ran correctly, but the malformed response format causes the gateway error.

Answer

The Lambda execution role lacks dynamodb:PutItem

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The API cache TTL is too short

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The API stage has X-Ray tracing enabled

Question 14

A Step Functions workflow calls three independent Lambda functions and should continue only after all results are available. Which state pattern should be used?

Accepted Answer

Parallel state. The Parallel state in AWS Step Functions is designed to execute multiple branches of work concurrently and then aggregate their outputs into a single array. This is exactly what is needed when three independent Lambda functions must all complete before the workflow continues, as the Parallel state waits for all branches to finish before proceeding to the next state.

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Choice state

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Wait state

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Fail state

Question 15

A developer needs an S3 upload workflow where clients upload large files directly to S3 without exposing AWS credentials through the browser. What should the backend generate?

Accepted Answer

Pre-signed URLs with appropriate expiration and object restrictions. Pre-signed URLs allow the backend to generate time-limited, permission-restricted URLs that clients can use to upload objects directly to S3 without exposing AWS credentials. The backend signs the URL with IAM credentials, and the client uses the URL to perform the PUT operation, ensuring secure, credential-free uploads.

Answer

Long-lived IAM access keys for each client

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A public-read bucket policy

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An S3 Inventory report