DVA-C02 Practice Test 8 — 10 Questions

Question 1

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?

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

Accepted Answer

Store the object key and event ID in a DynamoDB table and check for duplicates before processing. 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.

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

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Use an Amazon SQS FIFO queue as the event destination

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Enable S3 event notification filtering based on object size

Question 2

A developer is building a REST API using Amazon API Gateway and wants to transform the request data before sending it to the backend Lambda function. The transformation includes mapping query string parameters to a JSON body. Which API Gateway feature should be used?

Accepted Answer

Velocity Template Language (VTL) mapping templates. API Gateway uses Velocity Template Language (VTL) mapping templates to transform incoming request data, such as mapping query string parameters into a JSON body before passing it to the backend Lambda function. This feature allows you to define a template that extracts values from the request's query string parameters (e.g., `$input.params('paramName')`) and constructs a new JSON payload, enabling seamless integration with Lambda without modifying the client request.

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Lambda authorizer

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Request validator

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CORS configuration

Question 3

A developer is building a serverless application using an API Gateway HTTP API and Lambda. The developer needs to authenticate users with a JWT token. Which API Gateway feature should be used?

Accepted Answer

JWT Authorizer. API Gateway HTTP APIs support JWT Authorizers natively. This feature allows API Gateway to validate JSON Web Tokens (JWTs) directly without invoking a Lambda function, verifying the token's signature, expiry, and issuer against a configured identity provider (such as Amazon Cognito or any OIDC-compliant provider). This is the most efficient and cost-effective way to handle JWT authentication in HTTP APIs.

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Lambda Authorizer

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IAM Authorizer

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Amazon Cognito User Pools

Question 4

A developer is creating a new DynamoDB table to store order data. The orders have a unique order ID and are retrieved by order ID. Occasionally, the developer needs to query orders by customer ID. Which design approach would minimize costs and provide the fastest queries?

Accepted Answer

Use the order ID as the partition key and create a global secondary index on customer ID. Using the order ID as the partition key ensures the most efficient primary key access for the primary query pattern (retrieving by order ID). Creating a Global Secondary Index (GSI) on customer ID allows efficient querying by customer ID without scanning the base table, and GSIs have separate read/write capacity from the base table, so you only pay for the index when it is used. This design minimizes costs by avoiding unnecessary scans and provides the fastest queries for both access patterns.

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Use the customer ID as the partition key and order ID as the sort key

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Use the order ID as the partition key and scan the table for customer ID queries

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Use the customer ID as the partition key and create a local secondary index on order ID

Question 5

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.

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AWS AppConfig

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Amazon S3

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Amazon DynamoDB

Question 6

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.

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

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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 7

A developer is troubleshooting an AWS Lambda function that is triggered by an S3 event. The function occasionally fails with a timeout error. CloudWatch logs show that the timeout occurs during the processing of large files. The function has a memory setting of 128 MB and a timeout of 3 seconds. The developer wants to process large files without modifying the code. Which parameter should the developer adjust first?

Accepted Answer

Increase the function's memory. Increasing the function's memory is the correct first step because Lambda allocates CPU proportionally to memory, and more CPU reduces processing time for CPU-bound tasks like decompressing or parsing large files. This directly addresses the timeout by making the function complete faster, without requiring code changes. The current 128 MB setting is the minimum, which provides the least CPU, so even a modest increase can significantly reduce execution time.

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Increase the function's timeout

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Increase the function's reserved concurrency

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Increase the S3 event notification batch size

Question 8

A company wants to enforce multi-factor authentication (MFA) for all users accessing the AWS Management Console. The company has an existing IAM setup with users and groups. Which approach should the developer recommend to enforce MFA?

Accepted Answer

Attach an IAM policy to each user that denies all actions unless the user has MFA present.. It uses an IAM policy with a condition key (`aws:MultiFactorAuthPresent`) to deny all actions when MFA is not present. This is the standard AWS-recommended approach to enforce MFA for IAM users accessing the Management Console, as it applies a deny-all-except-MFA effect at the user level without requiring account-level changes.

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Enable MFA at the account level using the AWS Account settings.

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Enable MFA on the root user and require all users to use the root user credentials with MFA.

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Create a new IAM group for MFA users and add users to that group.

Question 9

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.

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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 10

A developer is using the AWS CLI to deploy a new version of a Lambda function. The developer runs the following command:

aws lambda update-function-code --function-name my-function --zip-file fileb://my-code.zip

After the command completes, the developer checks the function and sees that the code has been updated but the version number is still $LATEST. The developer wants to create a new version so that the previous version is preserved. What should the developer do next?

Accepted Answer

Run the publish-version command to create a new version from the updated $LATEST.. The `update-function-code` command without the `--publish` flag only updates the `$LATEST` version of the Lambda function. To create an immutable, numbered version that preserves the previous code, the developer must explicitly run the `publish-version` command, which takes the current `$LATEST` code and publishes it as a new version (e.g., version 2). This ensures the previous version (version 1) remains unchanged and can be referenced via its version ARN.

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Run the update-function-code command again with the --publish flag.

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Run the delete-function command and then create-function with the updated code.

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Run the update-function-configuration command to set the version number.