DVA-C02 Development with AWS Services Practice Test 22 — 15 Questions

Question 1

A Lambda function must retrieve feature flags at runtime with low latency and controlled rollout. Which AWS service is most appropriate?

Accepted Answer

AWS AppConfig. AWS AppConfig is the correct choice because it is purpose-built for managing application configuration at runtime, including feature flags, with support for controlled rollouts (e.g., percentage-based deployments, canary releases) and low-latency retrieval via the AppConfig agent or direct API calls. It integrates with AWS Lambda to fetch configuration values on-demand without requiring a full deployment, enabling dynamic feature toggling.

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AWS CloudFormation Parameters

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AWS IAM Access Analyzer

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Amazon Inspector

Question 2

A developer uses the AWS SDK to list thousands of DynamoDB items from a query. Only the first page is processed. What should be implemented?

Accepted Answer

Pagination using LastEvaluatedKey until no further key is returned. The DynamoDB Query API returns paginated results, with a maximum of 1 MB of data per page. The `LastEvaluatedKey` in the response indicates that more items exist. To retrieve all items, the application must check for `LastEvaluatedKey` and, if present, issue a subsequent Query request with the `ExclusiveStartKey` parameter set to that value, repeating until `LastEvaluatedKey` is no longer returned. This is the standard pagination pattern for DynamoDB.

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A larger Lambda memory setting only

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A global secondary index with the same key

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Strongly consistent reads on every request

Question 3

A Lambda function must share reusable validation code across several functions without packaging the same library into every deployment artifact. What should be used?

Accepted Answer

Lambda layer. Lambda layers allow you to centrally manage reusable code (e.g., validation libraries) and share it across multiple Lambda functions without packaging it into each deployment artifact. When you attach a layer to a function, the layer's content is extracted into the /opt directory, making it available at runtime. This avoids duplication and simplifies updates, as you only need to update the layer version rather than every function's deployment package.

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API Gateway usage plan

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S3 multipart upload

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CloudWatch metric filter

Question 4

An application uses DynamoDB Streams to trigger downstream processing. The processor must receive both old and new item images after updates. Which stream view type should be configured?

Accepted Answer

NEW_AND_OLD_IMAGES. B is correct because DynamoDB Streams must be configured with the NEW_AND_OLD_IMAGES stream view type to capture both the item's state before and after a write operation (update, insert, or delete). This ensures the downstream processor receives the complete old and new item data, which is required for use cases like auditing, change data capture, or reconciling state changes.

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KEYS_ONLY

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NEW_IMAGE only

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OLD_IMAGE only

Question 5

A REST API requires request validation before invoking Lambda to reduce unnecessary function executions for malformed payloads. Where should validation be configured?

Accepted Answer

In API Gateway request models and validators. API Gateway provides built-in request validation using models (JSON Schema) and validators. By configuring validation at the API Gateway layer, malformed payloads are rejected before they reach the Lambda function, reducing unnecessary invocations and associated costs. This is the correct approach because API Gateway acts as the entry point for REST APIs and can enforce payload structure without invoking the backend.

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Inside the Lambda timeout setting

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In the IAM execution role

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In the S3 bucket policy

Question 6

A developer wants a Lambda function to process SQS messages in batches but avoid losing the whole batch when only one record fails. Which feature should be enabled?

Accepted Answer

Partial batch response for SQS event source mapping. Partial batch response for SQS event source mapping allows the Lambda function to report which messages in a batch failed processing. When enabled, Lambda retries only the failed messages instead of the entire batch, preventing successful messages from being reprocessed or lost. This is achieved by returning a `batchItemFailures` array in the function's response, which tells Lambda which message IDs to retry.

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Reserved concurrency of one

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Maximum message size increase

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SQS short polling

Question 7

A service needs loosely coupled asynchronous communication where one producer sends events to many different AWS service targets using rules. Which service fits best?

Accepted Answer

Amazon EventBridge. Amazon EventBridge is a serverless event bus service that enables loosely coupled asynchronous communication. It allows a single producer to publish events, and then uses rules to route those events to multiple AWS service targets (e.g., Lambda, SQS, Step Functions) simultaneously, fulfilling the requirement exactly.

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Amazon EFS

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AWS CloudHSM

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AWS DataSync

Question 8

A Lambda function connects to an RDS database and causes too many database connections during traffic spikes. Which service should be introduced?

Accepted Answer

Amazon RDS Proxy. Amazon RDS Proxy sits between your Lambda function and the RDS database, managing a pool of established database connections. During traffic spikes, Lambda can rapidly scale up concurrent executions, each potentially opening a new database connection, which can exhaust the database's maximum connections. RDS Proxy reuses connections from the pool, reducing the number of open connections and preventing database overload, while also improving connection handling efficiency for serverless applications.

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AWS Glue Data Catalog

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Amazon Route 53 Resolver

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AWS WAF

Question 9

A developer must locally test a SAM-based Lambda function with an API event before deployment. Which tool command family is designed for this?

Accepted Answer

AWS SAM CLI local invoke/start-api. The AWS SAM CLI provides the `local invoke` and `local start-api` commands specifically for testing Lambda functions locally with simulated API Gateway events before deployment. `sam local start-api` creates a local HTTP server that mimics API Gateway, allowing developers to send requests to their Lambda functions as if they were deployed, while `sam local invoke` directly invokes the function with a specified event payload. This is the only tool family designed for local testing of SAM-based Lambda functions with API events.

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AWS Shield Advanced CLI

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AWS Organizations policy simulator

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Amazon Inspector SBOM export

Question 10

An application stores session data in DynamoDB and must expire sessions automatically after a timestamp. Which feature should be used?

Accepted Answer

DynamoDB Time to Live. DynamoDB Time to Live (TTL) allows you to define a timestamp attribute per item, and DynamoDB automatically deletes items once that timestamp is reached. This is the ideal feature for expiring session data without requiring custom scan-and-delete logic, reducing cost and operational overhead.

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DynamoDB global tables

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DynamoDB transactions

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DynamoDB export to S3

Question 11

A Lambda function needs temporary scratch space larger than the default while processing images. Which setting should be adjusted?

Accepted Answer

Ephemeral storage size for /tmp. Lambda functions have a default /tmp storage of 512 MB, which is insufficient for large image processing tasks. Adjusting the ephemeral storage size (up to 10,240 MB) provides the necessary scratch space for temporary files, such as intermediate image buffers or resized outputs, without requiring external storage like EFS.

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Reserved concurrency

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Function URL auth type

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Dead-letter queue target

Question 12

A developer is implementing S3 multipart upload for large files. Which two actions are required to complete the upload?

Accepted Answer

Upload all parts and keep their ETags/part numbers. During an S3 multipart upload, each part must be uploaded individually, and the response includes an ETag (a hash of the part) and a part number. These must be recorded and provided in the final request to assemble the object. Option D is correct because the CompleteMultipartUpload API call is required to signal S3 to combine all uploaded parts into the final object, using the list of ETags and part numbers.

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Enable S3 static website hosting

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Disable bucket encryption

Question 13

A DynamoDB query must support lookup by email address as well as by user ID. Which two changes may be required?

Accepted Answer

Create a secondary index with email as a key. A Global Secondary Index (GSI) or Local Secondary Index (LSI) on the email attribute allows DynamoDB to efficiently query by email address without scanning the entire table. Since the primary key is user ID, querying by email requires an index that uses email as the partition key or sort key. Option C is correct because specifying projection attributes limits the data returned from the index or table, reducing read capacity consumption and improving performance.

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Scan the full table for every login

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Disable partition keys

Question 14

A Lambda function processes a batch of SQS messages. Which two configurations reduce duplicate or failed-message impact?

Accepted Answer

Use a visibility timeout longer than expected processing time. A visibility timeout longer than the expected processing time prevents other consumers from reprocessing a message while it is still being handled, reducing duplicates. Option D is correct because a dead-letter queue captures messages that repeatedly fail processing, allowing analysis and preventing them from blocking the queue, while partial batch response enables the function to return a list of failed message IDs so that only those messages become visible again, reducing reprocessing of successful ones.

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Set visibility timeout to zero

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Disable the dead-letter queue

Question 15

Drag and drop the steps to configure an S3 bucket for static website hosting in the correct order.

Accepted Answer

Create an S3 bucket, enable static website hosting, configure index and error documents, set appropriate bucket policy for public read access, upload website content. First create the bucket, then enable static website hosting, configure index and error documents, set appropriate permissions, and finally upload content.

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Create an S3 bucket, configure index and error documents, enable static website hosting, set bucket policy, upload content

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Create an S3 bucket, enable static website hosting, set bucket policy, upload content, configure index and error documents

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Create an S3 bucket, set bucket policy, enable static website hosting, configure index and error documents, upload content