DVA-C02 Development with AWS Services Practice Test 31 — 15 Questions

Question 1

A developer is designing a system where an S3 bucket receives uploads, and each upload triggers a Lambda function to process the file. The processed output is stored in another S3 bucket. The developer notices that sometimes the same file is processed multiple times. How can this be prevented?

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

Accepted Answer

Make the Lambda function idempotent by checking if the object has already been processed using a DynamoDB table.. Making the Lambda function idempotent using a DynamoDB table ensures that even if the same S3 event is delivered multiple times (due to at-least-once delivery semantics) or if the same file is uploaded again, the function checks a unique identifier (such as the object key or hash) in DynamoDB before processing. If it has already been processed, the function can safely skip it. This is the standard architectural pattern for ensuring idempotency in serverless pipelines.

Answer

Use an SQS FIFO queue as the event destination and enable content-based deduplication.

Answer

Enable S3 bucket replication to another bucket and trigger Lambda from the replica.

Answer

Enable S3 bucket versioning and use 's3:ObjectCreated:Put' events.

Question 2

A developer needs to securely store database credentials for a Lambda function. The credentials must be automatically rotated every 30 days. Which service should be used?

Accepted Answer

AWS Secrets Manager. AWS Secrets Manager is the correct choice because it is specifically designed to securely store, manage, and automatically rotate database credentials and other secrets. It supports built-in rotation with AWS Lambda, allowing you to set a rotation schedule (e.g., every 30 days) without custom infrastructure. This service integrates directly with Amazon RDS, Redshift, and DocumentDB for seamless credential rotation.

Answer

AWS Key Management Service (KMS)

Answer

AWS Systems Manager Parameter Store

Answer

AWS CloudHSM

Question 3

A company is using Amazon CloudFront to distribute static content from an S3 bucket. The content is updated frequently, but users see stale content. The developer wants to ensure that new content is served as soon as possible after an update. Which action should be taken?

Accepted Answer

Create a CloudFront invalidation for the updated files.. CloudFront caches content at edge locations based on TTL settings. When content is updated in the S3 origin, existing cached copies remain stale until they expire or are explicitly invalidated. Creating a CloudFront invalidation for the updated files immediately removes the cached objects from all edge locations, forcing CloudFront to fetch the latest version from S3 on the next request. This ensures new content is served as soon as possible after an update.

Answer

Enable 'Origin Shield' to reduce the number of requests to S3.

Answer

Set the 'Minimum TTL' to 0 and 'Default TTL' to 0.

Answer

Set the 'Object Caching' to 0 in the CloudFront distribution.

Question 4

A developer is building a real-time chat application using WebSocket APIs in API Gateway and Lambda. The application must handle thousands of concurrent connections. Which TWO actions should the developer take to ensure the application scales properly?

Accepted Answer

Set the Lambda function's reserved concurrency to a high enough value.. Setting reserved concurrency ensures the Lambda function has enough allocated capacity to handle the high volume of concurrent WebSocket connections without being throttled by the account-level concurrency limit. Without reserved concurrency, the function could experience throttling errors (HTTP 429) during traffic spikes, causing dropped connections and poor user experience.

Answer

Use CloudFront to distribute the WebSocket endpoints.

Answer

Place the Lambda function in a VPC to improve security.

Answer

Enable API Gateway caching to reduce Lambda invocations.

Question 5

A developer is designing a serverless application that processes orders. The order processing must be transactional: either all steps succeed or none. Which TWO AWS services can be combined to achieve this?

Accepted Answer

AWS Step Functions. AWS Step Functions is correct because it provides a state machine that can coordinate multiple AWS services (e.g., Lambda, DynamoDB) in a defined workflow. It supports error handling, retries, and a 'catch' mechanism to roll back or compensate for failed steps, enabling transactional order processing where all steps succeed or none do.

Answer

Amazon SNS with filtering

Answer

Amazon SQS with FIFO queues

Answer

AWS Lambda with DLQ

Question 6

A company uses AWS CodePipeline to deploy a web application to an EC2 instance. The deployment often fails because the application is still running when new files are copied. Which THREE actions can be combined to achieve zero-downtime deployments?

Accepted Answer

Use AWS CodeDeploy with an in-place deployment configuration.. AWS CodeDeploy with an in-place deployment configuration can be combined with lifecycle hooks (such as BeforeInstall and AfterInstall) to stop the application before new files are copied and start it afterward, enabling zero-downtime deployments when properly orchestrated with a load balancer to drain traffic. Option B is correct because configuring EC2 instances behind an Auto Scaling group with a rolling update allows new instances to be launched with the updated application while old instances are terminated, ensuring continuous service availability. Option C is correct because defining an AppSpec file with BeforeInstall and AfterInstall hooks provides the mechanism to gracefully stop and start the application, preventing file conflicts and downtime.

Answer

Use AWS CodeBuild to build and deploy the application.

Answer

Use Amazon Inspector to check the application before deployment.

Question 7

A developer wants to upload a large file (5 GB) to an Amazon S3 bucket using the AWS SDK. Which approach is MOST efficient and resilient?

Accepted Answer

Use the Multipart Upload API to upload the file in parts.. The Multipart Upload API is specifically designed for large objects (over 100 MB, recommended for 5 GB). It allows uploading a file in parallel parts, which improves throughput and resilience by enabling retries of individual failed parts without restarting the entire upload. This approach also supports pausing and resuming uploads, making it the most efficient and resilient method for a 5 GB file.

Answer

Generate a presigned URL and use a third-party tool to upload.

Answer

Invoke an AWS Lambda function to upload the file.

Answer

Use the PutObject API call with the entire file.

Question 8

A developer is deploying a microservices architecture on Amazon ECS with Fargate. Each service needs to store sensitive configuration data such as database passwords. The developer wants to avoid hardcoding secrets in the application code. Which approach should the developer use?

Accepted Answer

Store the secrets in AWS Systems Manager Parameter Store or AWS Secrets Manager and reference them in the ECS task definition using the 'secrets' parameter.. AWS Systems Manager Parameter Store and AWS Secrets Manager are purpose-built services for securely storing and managing sensitive configuration data. By referencing secrets via the `secrets` parameter in the ECS task definition, the secrets are injected into the container at runtime without being exposed in the application code, task definition plaintext, or Docker image. This approach integrates natively with ECS Fargate and supports automatic rotation of secrets.

Answer

Store the secrets in an Amazon S3 bucket and use a pre-signed URL to download them at startup.

Answer

Define the secrets as environment variables in the ECS task definition.

Answer

Encrypt the secrets using AWS KMS and store the encrypted blob in a configuration file within the Docker image.

Question 9

A company is using Amazon CloudFront to serve content from an Application Load Balancer (ALB) origin. The ALB is configured as an internal load balancer in a VPC. Users are getting HTTP 502 errors when accessing the CloudFront distribution. What is the MOST likely cause?

Accepted Answer

The ALB is not internet-facing, so CloudFront cannot reach it.. The ALB is configured as an internal load balancer, meaning it only has private IP addresses and is accessible only within the VPC. CloudFront, being an AWS edge service outside the VPC, cannot route traffic to a private IP address without additional configuration such as a VPC origin or a public-facing ALB. This results in HTTP 502 errors because CloudFront cannot establish a connection to the origin.

Answer

The ALB has AWS WAF enabled, blocking CloudFront IP addresses.

Answer

The CloudFront distribution's cache behavior is set to cache all objects.

Answer

The CloudFront distribution is not associated with a VPN connection to the VPC.

Question 10

A developer needs to analyze real-time streaming data from thousands of devices. The data consists of JSON messages that must be processed and stored in Amazon S3. Which AWS service should the developer use to ingest and buffer the streaming data?

Accepted Answer

Amazon Kinesis Data Streams. Amazon Kinesis Data Streams is designed for real-time ingestion and buffering of large-scale streaming data, such as JSON messages from thousands of devices. It can capture and store data in shards for up to 365 days, allowing downstream consumers (e.g., Lambda, Kinesis Data Analytics) to process the data before storing it in Amazon S3. This makes it the correct choice for ingesting and buffering the streaming data before persistent storage.

Answer

Amazon S3

Answer

AWS Lambda

Answer

Amazon Simple Queue Service (SQS)

Question 11

A developer is building an application that uses Amazon DynamoDB as a data store. The application reads the same item frequently but writes rarely. The developer wants to reduce read costs. Which DynamoDB feature should the developer use?

Accepted Answer

DynamoDB Accelerator (DAX). DynamoDB Accelerator (DAX) is an in-memory cache that reduces read latency from single-digit milliseconds to microseconds. Since the application reads the same item frequently but writes rarely, DAX can serve repeated read requests from its cache, significantly reducing the number of read capacity units consumed against the DynamoDB table and thus lowering read costs.

Answer

DynamoDB Global Tables

Answer

DynamoDB Auto Scaling

Answer

Time to Live (TTL)

Question 12

A company has an AWS Lambda function that processes messages from an Amazon SQS queue. The function sometimes fails due to transient errors. The developer wants to ensure that failed messages are retried automatically and then sent to a dead-letter queue after three failed attempts. How should the developer configure this?

Accepted Answer

Configure the SQS queue with a redrive policy and a dead-letter queue. Set the maxReceiveCount to 3.. Amazon SQS supports a redrive policy that automatically moves messages to a dead-letter queue (DLQ) after a specified number of receive attempts. By setting maxReceiveCount to 3, the SQS queue will retry delivering the message to the Lambda function up to three times (including the initial attempt). After three failed processing attempts, the message is automatically sent to the configured DLQ. This approach decouples retry logic from the Lambda function itself and leverages SQS's built-in reliability features.

Answer

Enable Lambda function's DLQ and set the retry attempts to 3.

Answer

Configure the Lambda function's reserved concurrency to 0 and set the DLQ on the function.

Answer

Use an Amazon SNS topic to send failed messages to a DLQ after three Lambda invocations.

Question 13

A developer is using AWS CodePipeline to automate the deployment of a web application. The developer wants to run unit tests after the source stage and before deploying to a staging environment. Which action should the developer add to the pipeline?

Accepted Answer

AWS CodeBuild. AWS CodeBuild is the correct service to run unit tests in a CodePipeline because it provides a fully managed build environment that can execute test commands defined in a buildspec file. By adding a CodeBuild action to the pipeline after the source stage, the developer can run unit tests and fail the pipeline if tests do not pass, ensuring only validated code proceeds to the staging deployment.

Answer

AWS CodeCommit

Answer

AWS CloudFormation

Answer

AWS CodeDeploy

Question 14

A developer is designing a serverless application that uses Amazon API Gateway and AWS Lambda. The application needs to handle a sudden spike in traffic. The Lambda function performs CPU-intensive operations. What should the developer do to ensure the application scales without errors?

Accepted Answer

Configure the Lambda function with reserved concurrency and provisioned concurrency.. Reserved concurrency guarantees that the Lambda function has a dedicated pool of concurrency available to handle traffic spikes without being throttled by other functions in the account, while provisioned concurrency pre-warms execution environments to eliminate cold starts for CPU-intensive operations. This combination ensures that the application scales smoothly under sudden load without encountering Lambda throttling errors (HTTP 429) or latency spikes from cold starts.

Answer

Set the API Gateway throttling limits to a high value.

Answer

Use an Amazon SQS queue to buffer requests before processing.

Answer

Increase the Lambda function timeout to the maximum value.

Question 15

A developer is designing a mobile application that needs to upload files to Amazon S3. The developer wants to use temporary credentials to avoid storing long-term AWS credentials on the device. Which TWO services should the developer use together?

Accepted Answer

AWS Security Token Service (STS). AWS Security Token Service (STS) is used to generate temporary, limited-privilege credentials for accessing AWS resources, such as S3 buckets. Amazon Cognito provides identity pools that can automatically obtain and refresh STS tokens for authenticated users, eliminating the need to store long-term AWS credentials on the mobile device. Together, they enable secure, temporary credential management for file uploads.

Answer

Amazon S3 Transfer Acceleration

Answer

AWS Identity and Access Management (IAM)

Answer

AWS Key Management Service (KMS)