DVA-C01 : AWS Certified Developer Associate : Part 09
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A nightly batch job loads 1 million new records into a DynamoDB table. The records are only needed for one hour, and the table needs to be empty by the next night’s batch job.
Which is the MOST efficient and cost-effective method to provide an empty table?
- Use DeleteItem using a ConditionExpression.
- Use BatchWriteItem to empty all of the rows.
- Write a recursive function that scans and calls out DeleteItem.
- Create and then delete the table after the task has completed.
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A company has an application that logs all information to Amazon S3. Whenever there is a new log file, an AWS Lambda function is invoked to process the log files. The code works, gathering all of the necessary information. However, when checking the Lambda function logs, duplicate entries with the same request ID are found.
What is causing the duplicate entries?
- The S3 bucket name was specified incorrectly.
- The Lambda function failed, and the Lambda service retried the invocation with a delay.
- There was an S3 outage, which caused duplicate entries of the same log file.
- The application stopped intermittently and then resumed.
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A company maintains a REST service using Amazon API Gateway and the API Gateway native API key validation. The company recently launched a new registration page, which allows users to sign up for the service. The registration page creates a new API key using CreateApiKey and sends the new key to the user. When the user attempts to call the API using this key, the user receives a 403 Forbidden error. Existing users are unaffected and can still call the API.
What code updates will grant these new users access to the API?
- The createDeployment method must be called so the API can be redeployed to include the newly created API key.
- The updateAuthorizer method must be called to update the API’s authorizer to include the newly created API key.
- The importApiKeys method must be called to import all newly created API keys into the current stage of the API.
- The createUsagePlanKey method must be called to associate the newly created API key with the correct usage plan.
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A Developer is writing a mobile application that allows users to view images from an S3 bucket. The users must be able to log in with their Amazon login, as well as Facebook® and/or Google® accounts.
How can the Developer provide this authentication functionality?
- Use Amazon Cognito with web identity federation.
- Use Amazon Cognito with SAML-based identity federation.
- Use AWS IAM Access/Secret keys in the application code to allow Get* on the S3 bucket.
- Use AWS STS AssumeRole in the application code and assume a role with Get* permissions on the S3 bucket.
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A Developer has created a Lambda function and is finding that the function is taking longer to complete than expected. After some debugging, the Developer has discovered that increasing compute capacity would improve performance.
How can the Developer increase the Lambda compute resources?
- Run on a larger instance size with more compute capacity.
- Increase the maximum execution time.
- Specify a larger compute capacity when calling the Lambda function.
- Increase the allocated memory for the Lambda function.
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An e-commerce site allows returning users to log in to display customized web pages. The workflow is shown in the image below:
An application is running on EC2 instances. Amazon RDS is used for the database that stores user accounts and preferences. The website freezes or is slow to load while waiting for the login step to complete. The remaining components of the site are well-optimized.
Which of the following techniques will resolve this issue? (Choose two.)
- Implement the user login page as an asynchronous Lambda function.
- Use Amazon ElastiCache for MemCached to cache user data.
- Use an Amazon Application Load Balancer to load balance the traffic to the website.
- Call the database asynchronously so the code can continue executing.
- Batch login requests from hundreds of users together as a single read request to the database.
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A Developer is building a mobile application and needs any update to user profile data to be pushed to all devices accessing the specific identity. The Developer does not want to manage a back end to maintain the user profile data.
What is the MOST efficient way for the Developer to achieve these requirements using Amazon Cognito?
- Use Cognito federated identities.
- Use a Cognito user pool.
- Use Cognito Sync.
- Use Cognito events.
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A company is migrating a single-server, on-premises web application to AWS. The company intends to use multiple servers behind an Elastic Load Balancer (ELB) to balance the load, and will also store session data in memory on the web server. The company does not want to lose that session data if a server fails or goes offline, and it wants to minimize user’s downtime.
Where should the company move session data to MOST effectively reduce downtime and make users’ session data more fault tolerant?
- An Amazon ElastiCache for Redis cluster
- A second Amazon EBS volume
- The web server’s primary disk
- An Amazon EC2 instance dedicated to session data
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A Developer created configuration specifications for an AWS Elastic Beanstalk application in a file named healthcheckurl.yaml in the .ebextensions/directory of their application source bundle. The file contains the following:
After the application launches, the health check is not being run on the correct path, even though it is valid.
What can be done to correct this configuration file?
- Convert the file to JSON format.
- Rename the file to a .config extension.
- Change the configuration section from options_settings to resources.
- Change the namespace of the option settings to a custom namespace.
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A Developer is making changes to a custom application that is currently using AWS Elastic Beanstalk.
After the Developer completes the changes, what solutions will update the Elastic Beanstalk environment with the new application version? (Choose two.)
- Package the application code into a .zip file, and upload, then deploy the packaged application from the AWS Management Console
- Package the application code into a .tar file, create a new application version from the AWS Management Console, then update the environment by using AWS CLI
- Package the application code into a .tar file, and upload and deploy the packaged application from the AWS Management Console
- Package the application code into a .zip file, create a new application version from the packaged application by using AWS CLI, then update the environment by using AWS CLI
- Package the application code into a .zip file, create a new application version from the AWS Management Console, then rebuild the environment by using AWS CLI
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To include objects defined by the AWS Serverless Application Model (SAM) in an AWS CloudFormation template, in addition to Resources, what section MUST be included in the document root?
- Conditions
- Globals
- Transform
- Properties
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A company is using Amazon RDS MySQL instances for its application database tier and Apache Tomcat servers for its web tier. Most of the database queries from web applications are repeated read requests.
Use of which AWS service would increase in performance by adding in-memory store for repeated read queries?
- Amazon RDS Multi-AZ
- Amazon SQS
- Amazon ElastiCache
- Amazon RDS read replica
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A Developer is investigating an issue whereby certain requests are passing through an Amazon API Gateway endpoint /MyAPI, but the requests do not reach the AWS Lambda function backing /MyAPI. The Developer found that a second Lambda function sometimes runs at maximum concurrency allowed for the given AWS account.
How can the Developer address this issue?
- Manually reduce the concurrent execution limit at the account level
- Add another API Gateway stage for /MyAPI, and shard the requests
- Configure the second Lambda function’s concurrency execution limit
- Reduce the throttling limits in the API Gateway /MyAPI endpoint
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A Developer must analyze performance issues with production-distributed applications written as AWS Lambda functions. These distributed Lambda applications invoke other components that make up the applications.
How should the Developer identify and troubleshoot the root cause of the performance issues in production?
- Add logging statements to the Lambda functions, then use Amazon CloudWatch to view the logs.
- Use AWS CloudTrail and then examine the logs.
- Use AWS X-Ray, then examine the segments and errors.
- Run Amazon Inspector agents and then analyze performance.
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A Developer wants to debug an application by searching and filtering log data. The application logs are stored in Amazon CloudWatch Logs. The Developer creates a new metric filter to count exceptions in the application logs. However, no results are returned from the logs.
What is the reason that no filtered results are being returned?
- A setup of the Amazon CloudWatch interface VPC endpoint is required for filtering the CloudWatch Logs in the VPC
- CloudWatch Logs only publishes metric data for events that happen after the filter is created
- The log group for CloudWatch Logs should be first streamed to Amazon Elasticsearch Service before metric filtering returns the results
- Metric data points for logs groups can be filtered only after they are exported to an Amazon S3 bucket
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An e-commerce web application that shares session state on-premises is being migrated to AWS. The application must be fault tolerant, natively highly scalable, and any service interruption should not affect the user experience.
What is the best option to store the session state?
- Store the session state in Amazon ElastiCache
- Store the session state in Amazon CloudFront
- Store the session state in Amazon S3
- Enable session stickiness using elastic load balancers
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A Developer is creating a template that uses AWS CloudFormation to deploy an application. This application is serverless and uses Amazon API Gateway, Amazon DynamoDB, and AWS Lambda.
Which tool should the Developer use to define simplified syntax for expressing serverless resources?
- CloudFormation serverless intrinsic functions
- AWS serverless express
- An AWS serverless application model
- A CloudFormation serverless plugin
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A Developer has a stateful web server on-premises that is being migrated to AWS. The Developer must have greater elasticity in the new design.
How should the Developer re-factor the application to make it more elastic? (Choose two.)
- Use pessimistic concurrency on Amazon DynamoDB
- Use Amazon CloudFront with an Auto Scaling group
- Use Amazon CloudFront with an AWS Web Application Firewall
- Store session state data in an Amazon DynamoDB table
- Use an ELB with an Auto Scaling group
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A company needs to distribute firmware updates to its customers around the world.
Which service will allow easy and secure control of the access to the downloads at the lowest cost?
- Use Amazon CloudFront with signed URLs for Amazon S3
- Create a dedicated Amazon CloudFront Distribution for each customer
- Use Amazon CloudFront with AWS Lambda@Edge
- Use Amazon API Gateway and AWS Lambda to control access to an S3 bucket
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A company is running an application built on AWS Lambda functions. One Lambda function has performance issues when it has to download a 50MB file from the Internet in every execution. This function is called multiple times a second.
What solution would give the BEST performance increase?
- Cache the file in the /tmp directory
- Increase the Lambda maximum execution time
- Put an Elastic Load Balancer in front of the Lambda function
- Cache the file in Amazon S3
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