DVA-C02 Development with AWS Services Practice Test 21 — 15 Questions

Question 1

A developer is using AWS Step Functions to orchestrate a workflow that includes a Lambda function for data transformation. The Lambda function occasionally times out after 15 seconds. The Step Function execution fails with a 'States.Timeout' error. The developer wants to retry the Lambda task up to 3 times with exponential backoff. Which configuration should the developer add to the state definition in the Amazon States Language (ASL)?

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

Accepted Answer

"Retry": [ { "ErrorEquals": ["States.Timeout"], "IntervalSeconds": 1, "BackoffRate": 2, "MaxAttempts": 3 } ]. It defines a retry policy for the 'States.Timeout' error, which is the error that occurs when the Lambda function times out. The configuration sets a 1-second initial interval, doubles the interval on each retry (BackoffRate of 2), and allows up to 3 retries, matching the requirement exactly.

Answer

"Retry": [ { "ErrorEquals": ["States.Timeout"], "IntervalSeconds": 2, "BackoffRate": 3, "MaxAttempts": 5 } ]

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"Retry": [ { "ErrorEquals": ["States.Timeout"], "IntervalSeconds": 1, "BackoffRate": 2, "MaxAttempts": 2 } ]

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"Retry": [ { "ErrorEquals": ["Lambda.ServiceException"], "IntervalSeconds": 1, "BackoffRate": 2, "MaxAttempts": 3 } ]

Question 2

A company uses Amazon API Gateway to expose a REST API. The API uses a Lambda authorizer to validate JWT tokens. Recently, the API has been returning 401 Unauthorized errors for valid tokens. The developer notices that the tokens are signed with a new key but the authorizer still uses the old key. What is the MOST efficient way to update the authorizer with the new key?

Accepted Answer

Modify the Lambda authorizer to fetch the public key from a well-known URL at runtime.. Fetching the public key from a well-known URL (e.g., the JWKS endpoint) at runtime allows the Lambda authorizer to automatically use the latest signing key without manual intervention. This approach decouples key rotation from the authorizer code, ensuring that valid tokens signed with the new key are accepted immediately. It is the most efficient method as it avoids redeployments, environment variable updates, or recreating the authorizer.

Answer

Update the API Gateway stage deployment to redeploy the API.

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Delete and recreate the API Gateway authorizer with the new key.

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Update the Lambda authorizer's environment variable with the new key and publish a new version.

Question 3

A developer needs to send large files (up to 5 GB) from a web application to Amazon S3. The application runs on EC2 instances. Which approach is MOST efficient and reliable?

Accepted Answer

Use S3 multipart upload to upload the file in parts.. S3 multipart upload is the most efficient and reliable approach for uploading large files (up to 5 GB) because it allows the file to be split into smaller parts that can be uploaded in parallel, improving throughput and resilience. If a part fails, only that part needs to be retried, not the entire file, and the upload can be paused and resumed. This is the recommended AWS method for objects larger than 100 MB and is required for objects over 5 GB.

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Save the file to EC2 instance store and then copy to S3.

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Upload the file as a single S3 PutObject operation.

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Use S3 Transfer Acceleration to upload the file.

Question 4

A developer is building a serverless application that processes images uploaded to an S3 bucket. The bucket triggers a Lambda function that creates a thumbnail and stores it in another S3 bucket. The developer notices that the Lambda function is invoked multiple times for the same object, causing duplicate thumbnails. What is the MOST likely cause?

Accepted Answer

S3 event notifications are eventually consistent and may deliver duplicates.. Amazon S3 event notifications are designed to provide at-least-once delivery. This means that while most events are delivered exactly once, duplicate event notifications can occasionally occur. To handle this, the Lambda function should be designed to be idempotent, ensuring that processing the same event multiple times does not cause unintended side effects (like duplicate thumbnails).

Answer

The Lambda function is configured with a DLQ that causes retries.

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The Lambda function is idempotent and should handle duplicates.

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The S3 bucket has multiple event notifications that trigger the same Lambda function.

Question 5

Which TWO AWS services can be used to decouple components of a microservices architecture?

Accepted Answer

Amazon EventBridge. Amazon EventBridge (Option B) is correct because it provides a serverless event bus that decouples microservices by allowing them to communicate asynchronously via events. Services publish events to EventBridge, and other services consume them without direct coupling, enabling loose coupling and scalability.

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Amazon Route 53

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Elastic Load Balancing

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Amazon CloudWatch

Question 6

Which THREE actions can a developer take to improve the cold start latency of an AWS Lambda function?

Accepted Answer

Use a language runtime with faster startup time, such as Python or Node.js.. Python and Node.js use interpreted runtimes with faster initialization times compared to compiled runtimes like Java or .NET. These runtimes have smaller binary sizes and lower startup overhead, reducing the time from invocation to execution start, which directly improves cold start latency.

Answer

Place the Lambda function inside a VPC.

Answer

Increase the function's timeout setting.

Question 7

A company is building a serverless application using AWS Lambda and Amazon API Gateway. The application needs to process user uploads to an S3 bucket. The Lambda function should be invoked only when new objects are created in the bucket. Which service should be used to trigger the Lambda function?

Accepted Answer

Amazon S3 event notifications. Amazon S3 event notifications can be configured to trigger AWS Lambda functions when specific events occur in an S3 bucket, such as when a new object is created (e.g., s3:ObjectCreated:*). This is the native and most direct way to invoke a Lambda function in response to S3 object uploads. It requires no additional polling or infrastructure and is highly scalable.

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Amazon Kinesis Data Streams

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Amazon CloudWatch Events

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Amazon Simple Queue Service (SQS)

Question 8

A developer needs to store configuration parameters securely for a Lambda function. The parameters include database credentials and API keys. Which AWS service should be used?

Accepted Answer

AWS Secrets Manager. AWS Secrets Manager is the correct choice because it is purpose-built for securely storing, rotating, and managing sensitive configuration parameters such as database credentials and API keys throughout their lifecycle. It offers automatic rotation of secrets with built-in integration for Amazon RDS, Redshift, and DocumentDB, and enforces fine-grained access control via IAM policies. This makes it the most suitable service for the developer's requirement of securely storing and managing database credentials and API keys for a Lambda function.

Answer

AWS Systems Manager Parameter Store

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Amazon DynamoDB with encryption

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Amazon S3 with server-side encryption

Question 9

A developer notices that an AWS Lambda function is timing out after 15 seconds. The function makes HTTP requests to an external API. How can the developer resolve this issue without changing the function code?

Accepted Answer

Increase the timeout setting of the Lambda function. The Lambda function is timing out because its configured execution timeout (15 seconds) is too short for the HTTP requests to the external API to complete. Increasing the timeout setting (up to the maximum limit of 15 minutes) allows the function to run longer and wait for the API response, resolving the timeout without modifying the code. This is a configuration change in the Lambda function settings, not a code change.

Answer

Increase the reserved concurrency

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Place the Lambda function in a VPC

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Decrease the memory allocation of the Lambda function

Question 10

A company is using Amazon API Gateway to expose a REST API. The API must authenticate requests using an external OAuth 2.0 provider. Which API Gateway feature should be used?

Accepted Answer

Lambda authorizer. A Lambda authorizer (formerly known as a custom authorizer) allows you to implement custom authentication logic using an external OAuth 2.0 provider. The Lambda function receives the OAuth 2.0 bearer token from the request, validates it against the external provider's token introspection endpoint or by verifying the JWT signature, and returns an IAM policy that grants or denies access to the API Gateway method.

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IAM authorization

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Resource policy

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Amazon Cognito User Pools

Question 11

A developer is building an application that needs to send email notifications to users. Which AWS service is designed for sending transactional emails?

Accepted Answer

Amazon Simple Email Service (SES). Amazon Simple Email Service (SES) is specifically designed for sending transactional emails, such as order confirmations, password resets, and marketing communications. It provides a reliable, scalable SMTP interface or API to send high-deliverability emails, with features like dedicated IP addresses and feedback loops. This makes it the correct choice for an application that needs to send email notifications directly to users.

Answer

AWS Lambda

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Amazon Simple Notification Service (SNS)

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Amazon Simple Queue Service (SQS)

Question 12

A developer is using AWS CodeBuild to build a Java application. The build fails with 'OutOfMemoryError: Java heap space'. How can the developer fix this without changing the source code?

Accepted Answer

Increase the compute type of the build project. AWS CodeBuild allows you to increase the compute type (e.g., from BUILD_GENERAL1_SMALL to BUILD_GENERAL1_MEDIUM or LARGE), which provides more memory and CPU resources. This directly addresses the 'OutOfMemoryError: Java heap space' by giving the JVM more physical memory to work with, without requiring any source code changes.

Answer

Add -Xmx1024m to the buildspec commands

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Change the build image to a smaller one

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Set the memory parameter in the build project

Question 13

A developer wants to debug an AWS Lambda function by viewing real-time logs. Which AWS service should the developer use?

Accepted Answer

Amazon CloudWatch Logs. Amazon CloudWatch Logs is the correct service because AWS Lambda automatically streams all execution logs, including real-time output from console.log() statements and any errors, to CloudWatch Logs. The developer can use the CloudWatch Logs console or the `aws logs tail` command to view these logs in near real-time, enabling effective debugging of function behavior as it executes.

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AWS X-Ray

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Amazon S3

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AWS CloudTrail

Question 14

A developer is using Amazon DynamoDB as the data store for a web application. The application experiences frequent throttling errors. Which action can reduce throttling without changing the application code?

Accepted Answer

Enable DynamoDB Auto Scaling. DynamoDB Auto Scaling automatically adjusts the provisioned throughput capacity based on actual traffic patterns, using the AWS Application Auto Scaling service. This prevents throttling by increasing capacity during demand spikes and reduces costs by scaling down during low traffic, all without requiring any code changes.

Answer

Add a secondary index

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Decrease the provisioned write capacity

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Increase the provisioned read capacity only

Question 15

A developer is designing a serverless application that uses AWS Lambda and Amazon DynamoDB. The application needs to handle high traffic spikes without data loss. Which TWO actions should the developer take?

Accepted Answer

Enable DynamoDB Auto Scaling. Option A (Enable DynamoDB Auto Scaling) is correct because DynamoDB Auto Scaling automatically adjusts provisioned read/write capacity in response to traffic spikes, ensuring the table can absorb sudden load without throttling or data loss. Option D (Use Amazon SQS to buffer requests to Lambda) is correct because placing an SQS queue between the request source and Lambda decouples the components, buffers bursts of traffic, and provides durable at-least-once delivery so requests are not lost if Lambda throttles or fails. Option B is incorrect because Provisioned IOPS is an EBS storage feature, not a DynamoDB capacity mode, and does not address DynamoDB throughput scaling. Option C is incorrect because DynamoDB Streams captures item-level changes for change data capture and triggers, but it does not itself handle traffic spikes or prevent data loss under load. Option E is incorrect because simply raising the Lambda concurrency limit to the maximum does not buffer requests or guarantee delivery; without a queue, excess invocations can still be throttled and dropped.

Answer

Use Provisioned IOPS for DynamoDB

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Enable DynamoDB Streams

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Increase the Lambda concurrency limit to the maximum