DVA-C02 Practice Exam 69 — 20 Questions

Question 1

A developer is building a serverless application using AWS Lambda and Amazon DynamoDB. The application needs to store and retrieve session data. The session data has a TTL of 30 minutes. Which DynamoDB feature should the developer use to automatically delete expired items?

Accepted Answer

Use DynamoDB Time to Live (TTL) to set an expiry time attribute that DynamoDB automatically deletes when the TTL is reached.. DynamoDB Time to Live (TTL) is the correct feature because it allows you to define a per-item timestamp attribute. When that timestamp is reached, DynamoDB automatically deletes the item without any additional cost or custom code. This directly meets the requirement to automatically delete expired session data after 30 minutes.

Answer

Use DynamoDB Streams to capture expired items and trigger a Lambda function for deletion.

Answer

Use DynamoDB Global Tables to replicate data to another region and then set a TTL on the replica.

Answer

Use DynamoDB Accelerator (DAX) to cache the data and expire it based on a cache TTL.

Question 2

A company wants to build a RESTful API that handles file uploads. The API needs to support multipart/form-data content type. The developer is using Amazon API Gateway and AWS Lambda. Which approach should the developer use to handle file uploads efficiently?

Accepted Answer

Use API Gateway to generate a presigned S3 URL, and have the client upload directly to S3. The Lambda function can then process the file asynchronously.. Option C is correct because it offloads the file upload to Amazon S3 directly via a presigned URL, which avoids the 10 MB payload limit and 29-second timeout of API Gateway and Lambda for large files. The client uploads the file to S3, and a separate Lambda function processes the file asynchronously, making the solution efficient and scalable for multipart/form-data uploads.

Answer

Configure API Gateway to pass the entire request body to Lambda, and process the file within the Lambda function.

Answer

Create a Lambda function that accepts the file and uploads it to S3 using the AWS SDK.

Answer

Use an EC2 instance to host a custom web server that accepts file uploads and writes to S3.

Question 3

A developer is building a microservices application that processes event messages from multiple sources. The application requires at-least-once delivery, but message ordering is not important. Which Amazon SQS queue type should the developer use?

Accepted Answer

Standard queue. Amazon SQS Standard queues provide at-least-once delivery and best-effort ordering, making them ideal for microservices that can tolerate duplicate messages and do not require strict message sequencing. Since the application processes events from multiple sources and message ordering is not important, a Standard queue meets the requirements without the throughput limitations of FIFO queues.

Answer

FIFO queue

Answer

Dead-letter queue

Answer

Delay queue

Question 4

A developer is building a REST API using Amazon API Gateway and AWS Lambda. The API receives a large number of requests with duplicate payloads from the same client within a short time window. To reduce Lambda invocations and improve performance, the developer wants to return the previously computed response for identical requests based on a unique client ID in the header. How can the developer achieve this using API Gateway features?

Accepted Answer

Enable API Gateway caching on the stage and configure the client ID header as a cache key parameter. Set a cache TTL of 5 minutes.. Option A is correct because API Gateway caching allows you to store responses for a configurable TTL and use the client ID header as a cache key parameter. This means that when a request with the same client ID arrives within the TTL window, API Gateway returns the cached response directly without invoking the Lambda function, reducing invocations and improving performance.

Answer

Configure a usage plan with a quota and throttle settings to limit requests per client ID.

Answer

Use request validation to reject requests that have the same client ID within 5 minutes.

Answer

Reduce the Lambda function's batch size to 1 and implement caching logic inside the function using an external cache like ElastiCache.

Question 5

A developer is building a RESTful API using Amazon API Gateway (HTTP API) and AWS Lambda. The API receives a large number of requests with duplicate payloads within a short time window. To improve performance and reduce costs, the developer wants to ensure that if the same request (based on a unique client ID) is sent within 5 minutes, the Lambda function is not invoked again, and the previously calculated response is returned. Which API Gateway feature should the developer use?

Accepted Answer

Enable API caching on the stage with a TTL of 300 seconds and configure the client ID as a cache key parameter.. Option A is correct because API Gateway's caching feature stores responses from your endpoint for a specified time-to-live (TTL). By setting the TTL to 300 seconds (5 minutes) and configuring the client ID as a cache key parameter, API Gateway will use the client ID to uniquely identify requests. If a request with the same client ID arrives within the TTL window, API Gateway returns the cached response without invoking the Lambda function, reducing costs and improving performance.

Answer

Enable request validation to reject duplicate requests.

Answer

Configure a usage plan with a throttle rate to limit requests from each client.

Answer

Enable stage variables to store the previous response.

Question 6

A developer is building a serverless application that processes orders. An order is placed and an event is published to an Amazon SNS topic. The SNS topic has multiple subscribers, including an SQS queue for order processing and a Lambda function for sending notifications. The developer wants to ensure that the SQS queue receives all messages reliably, even if the processing Lambda function fails temporarily. Which configuration should the developer set?

Accepted Answer

Enable a dead-letter queue on the SQS queue. A dead-letter queue (DLQ) on the SQS queue ensures that messages that cannot be processed successfully after the configured number of retries (maxReceiveCount) are moved to a separate queue for later analysis or reprocessing. This prevents message loss when the Lambda function fails temporarily, as the SQS queue will continue to receive messages from SNS reliably, and only messages that exceed the retry limit are redirected to the DLQ.

Answer

Enable SNS delivery retries for HTTP endpoints

Answer

Set the SQS queue's visibility timeout to a value greater than the Lambda function's processing time

Answer

Configure the SNS topic to use server-side encryption

Question 7

A developer is building a serverless REST API using Amazon API Gateway and AWS Lambda. The API should return JSON responses to client requests. The developer is using the Lambda proxy integration. What is the simplest way to return a JSON response from the Lambda function?

Accepted Answer

Return a dictionary containing 'statusCode', 'headers', and 'body' with 'body' as a JSON string.. With Lambda proxy integration, API Gateway passes the entire request to the Lambda function and expects the function to return a specific response format. The simplest way to return a JSON response is to return a dictionary (or object) containing 'statusCode', 'headers', and 'body', where 'body' is a JSON string. This format is required by API Gateway to correctly interpret the Lambda output and forward it to the client.

Answer

Return a string from the Lambda handler.

Answer

Use API Gateway integration response and mapping templates to transform the Lambda output.

Answer

Return a JSON object from Lambda and set a Content-Type header in the API Gateway method response.

Question 8

A developer is building an AWS Lambda function that needs to retrieve a database password securely. The password is stored in AWS Secrets Manager and is rotated every 30 days. The function must minimize the number of API calls to Secrets Manager. Which approach should the developer use?

Accepted Answer

Retrieve the secret from Secrets Manager once outside the handler function, cache it in a global variable, and refresh the cache if the secret fails.. Option C is correct because it retrieves the secret once during the Lambda cold start (outside the handler), caches it in a global variable, and only refreshes the cache if the secret fails (e.g., due to rotation). This minimizes API calls to Secrets Manager while still handling secret rotation gracefully, as the cached secret remains valid until a failure occurs.

Answer

Store the database password as an encrypted environment variable in the Lambda function.

Answer

Call Secrets Manager on every invocation to get the latest secret.

Answer

Use AWS Systems Manager Parameter Store SecureString instead of Secrets Manager.

Question 9

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.

Answer

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 10

A developer is building a serverless application that uses Amazon DynamoDB. The application needs to retrieve an item by its primary key frequently. Which DynamoDB API call should the developer use to achieve the lowest latency?

Accepted Answer

GetItem. The GetItem API call is the most efficient way to retrieve a single item by its primary key in DynamoDB, as it directly accesses the item using the hash key (and optionally the sort key) with consistent, single-digit millisecond latency. Unlike Scan or Query, GetItem does not need to evaluate any conditions or filter through other items, making it the lowest-latency option for this specific use case.

Answer

Scan

Answer

Query

Answer

BatchGetItem

Question 11

A developer is building a serverless application using AWS Lambda and Amazon API Gateway. The API requires that the same Lambda function handle different HTTP methods (GET, POST, DELETE) for the same resource. The developer wants to minimize code and configuration. Which integration type should the developer use?

Accepted Answer

Lambda proxy integration. Lambda proxy integration (option A) is correct because it automatically passes the entire HTTP request (method, headers, query parameters, path parameters) to the Lambda function as a single event object, allowing the same function to inspect the `httpMethod` field and branch logic for GET, POST, DELETE without any additional API Gateway mapping or transformation configuration. This minimizes both code (the function handles routing internally) and configuration (no need to define separate integration requests/responses per method).

Answer

Lambda custom integration

Answer

HTTP integration

Answer

Mock integration

Question 12

A developer is building a web application that requires user authentication. The application will run on Amazon EC2 instances behind an Application Load Balancer. The developer wants to offload authentication to a managed service that supports social login providers. Which AWS service should the developer use?

Accepted Answer

Amazon Cognito. Amazon Cognito is the correct choice because it is a fully managed identity service designed for web and mobile applications, providing user authentication, authorization, and support for social login providers (e.g., Google, Facebook, Amazon) via OAuth 2.0 and OpenID Connect. It offloads the entire authentication workflow from the EC2 instances and ALB, integrating seamlessly with the ALB's authentication action to validate tokens before traffic reaches the application.

Answer

AWS Identity and Access Management (IAM)

Answer

AWS Directory Service

Answer

AWS Single Sign-On

Question 13

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. Option A is correct because 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.

Answer

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

Answer

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

Answer

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

Question 14

A developer is building an application that needs to store session state data for a web application running on multiple EC2 instances behind an ALB. 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 a managed in-memory cache (e.g., Redis or Memcached) that is ideal for storing ephemeral session state data. Session data is temporary and must be shared across multiple EC2 instances behind an ALB, and ElastiCache offers sub-millisecond latency and automatic key expiration, ensuring data is not persisted if an instance terminates. This aligns with the requirement for non-persistent, high-performance session storage that survives individual instance failures.

Answer

Amazon RDS

Answer

Amazon DynamoDB

Answer

Amazon S3

Question 15

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.

Answer

Standard queue.

Answer

Dead-letter queue.

Answer

Delay queue.

Question 16

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.

Answer

Reserved concurrency

Answer

Function URL auth type

Answer

Dead-letter queue target

Question 17

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. Option B is correct because 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.

Answer

Set visibility timeout to zero

Answer

Disable the dead-letter queue

Question 18

A developer is building a REST API using Amazon API Gateway and AWS Lambda. The API must support request validation, request throttling, and API keys. Which API Gateway feature should the developer use to enforce a daily request limit for each API key?

Accepted Answer

Usage plans. Usage plans in API Gateway allow you to set throttling and quota limits per API key, enabling daily request limits for each key. This feature is specifically designed to control usage by associating API keys with a plan that defines rate limits and quotas, such as a daily request cap. Option A is correct because it directly addresses the requirement to enforce a daily request limit per API key.

Answer

API keys

Answer

Throttling settings at the method level

Answer

AWS WAF

Question 19

A developer is writing an AWS Lambda function that processes files uploaded to an S3 bucket. The function should only be triggered when a new object is created in a specific subfolder (e.g., /uploads/). Which S3 event notification configuration should the developer use?

Accepted Answer

Configure the event notification with a prefix filter set to 'uploads/' and event type 's3:ObjectCreated:*'.. Option A is correct because S3 event notifications support prefix filtering, which allows you to specify a key prefix (e.g., 'uploads/') so that only object creation events in that subfolder trigger the Lambda function. By setting the event type to 's3:ObjectCreated:*', the function responds to all object creation operations (PUT, POST, Copy, etc.) within the filtered path, meeting the requirement precisely without unnecessary invocations.

Answer

Configure a single event notification for all objects and filter on the prefix inside the Lambda function.

Answer

Configure the event notification using object tags to filter events.

Answer

Use AWS CloudTrail to detect S3 PutObject events and trigger Lambda.

Question 20

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.

Answer

S3 Inventory

Answer

S3 Transfer Acceleration

Answer

S3 Batch Operations