Section-Based – Refactoring (CDA)

A developer is moving a legacy web application from their on-premises data center to AWS. The application is used simultaneously by thousands of users, and their session states are stored in memory. The on-premises server usually reaches 100% CPU Utilization every time there is a surge in the number of people accessing the application.

Which of the following is the best way to re-factor the performance and availability of the application’s session management once it is migrated to AWS?

A Software Engineer is developing an application that will be hosted on an Amazon EC2 instance and read messages from a standard Amazon SQS queue. The average time that it takes for the producers to send a new message to the queue is 10 seconds.

Which of the following is the MOST efficient way for the application to query the new messages from the queue?

A serverless application composed of Lambda, API Gateway, and DynamoDB has been running without issues for quite some time. As part of the IT compliance of the company, a developer was instructed to ensure that all of the new changes made to the items in DynamoDB are recorded and stored in another DynamoDB table in another region.

In this scenario, which of the following is the MOST ideal way to comply with the requirements?

A mobile game has a serverless backend consisting of an API Gateway backed by Lambda functions and a DynamoDB table in provisioned capacity mode, where player data is stored. While the game has maintained a consistent level of traffic, recent growth in the player base has caused response times to slow down. To improve performance, the developer wants to reduce the number of database queries for data that rarely change.

What approach can the developer take to achieve this goal cost-effectively and with less development overhead?

A company selling smart security cameras uses an S3 bucket behind a CloudFront web distribution to store its static content, which it shares with customers worldwide. The company has recently released a new firmware update intended only for its premium customers, and unauthorized access should be denied with a user authentication process that has minimal latency.

How can a developer refactor the current setup to achieve this requirement with the MOST efficient solution?

An application hosted in an Amazon ECS Cluster processes a large data stream and stores the result in a DynamoDB table. There is an urgent requirement to detect new entries in the table and automatically trigger a Lambda function to run some verification tests on the processed data.

Which of the following options can satisfy the requirement with minimal configuration?

A developer is building a photo-sharing application that automatically enhances images uploaded by users to Amazon S3. When a user uploads an image, its S3 path is sent to an image-processing application hosted on AWS Lambda. The Lambda function applies the selected filter to the image and stores it back to S3.

If the upload is successful, the application will return a prompt telling the user that the request has been accepted. The entire processing typically takes an average of 5 minutes to complete, which causes the application to become unresponsive.

Which of the following is the MOST suitable and cost-effective option which will prevent the application from being unresponsive?

A developer has an application that uses a Lambda function to process data from an Aurora MySQL DB Instance in a Virtual Private Cloud (VPC). The database throws a MySQL: ERROR 1040: Too many connections error whenever there is a surge in incoming traffic.

Which is the most suitable solution for resolving the issue?

A website is hosted in an Auto Scaling group of EC2 instances behind an Application Load Balancer. It also uses CloudFront with a default domain name to distribute its static assets and dynamic contents. However, the website has a poor search ranking as it doesn’t use a secure HTTPS/SSL on its site.

Which are the possible solutions that the developer can implement in order to set up HTTPS communication between the viewers and CloudFront? (Select TWO.)

A developer is managing a distributed system that consists of an Application Load Balancer, an SQS queue, and an Auto Scaling group of EC2 instances. The system has been integrated with CloudFront to better serve clients worldwide. To enhance the security of the in-flight data, the developer was instructed to establish an end-to-end SSL connection between the origin and the end-users.

Which TWO options will allow the developer to meet this requirement using CloudFront? (Select TWO.)

A reporting application is hosted in AWS Elastic Beanstalk and uses Amazon DynamoDB as its database. If a user requests data, the application scans the entire table and returns the requested data. The table is expected to grow due to the surge of new users and the increase in requests for reports in the coming weeks.

Which of the following should be done as a preparation to improve the application’s performance with minimal cost? (Select TWO.)

A developer is instructed to configure a worker daemon to queue messages based on a specific schedule using a worker environment hosted in Elastic Beanstalk. Periodic tasks should be defined to automatically add jobs to your worker environment’s queue at regular intervals.

Which configuration file should the developer add to the source bundle to meet the above requirement?

A DynamoDB table has several top-level attributes such as id, course_id, course_title, price, rating and many others. The database queries of your application returns all of the item attributes by default but you only want to fetch specific attributes such as the course_id and price per request.

As the developer, how can you refactor your application to accomplish this requirement?

A Lambda function downloads the same 250 MB file between invocations and stores it in memory for processing. This leads to frequent timeouts and negatively impacts the performance of the serverless application.

Which change should be made to resolve the issue most effectively?

Using AWS SAM, a developer recently deployed a serverless application consisting of Lambda functions, API Gateway, Kinesis Data stream, and a DynamoDB table. The application has worked fine for a few days, but lately, there were a lot of ProvisionedThroughputExceeded exceptions being returned by DynamoDB. The developer also noticed that there’s a sudden increase in read capacity units (RCU) usage whenever this issue happens.

How should the developer refactor the application to find items based on primary key values and use the LEAST amount of RCU?

A company has an AWS Amplify application, relying on Amazon Cognito for user authentication. Multi-factor authentication (MFA) is disabled for their User Pool. There has been a recent data breach in a popular website. The company is worried that attackers might exploit compromised email addresses and passwords to sign into their applications. For this reason, they want to enforce MFA only on users with suspicious login attempts.

How can the company satisfy these requirements

An application is sending thousands of log files to an S3 bucket everyday. The request to retrieve the list of objects using the AWS CLI aws s3api list-objects command is timing out due to the high volume of data being fetched. In order to rectify this issue, you have to use pagination to control the number of results returned on your request.

Which of the following parameters should you include in CLI command for this scenario? (Select TWO.)

A developer has a set of EC2 instances that runs the Amazon Kinesis Client Library to process a data stream in AWS. Based on the custom metrics, it shows that the instances are maxing out their CPU Utilization, and there are insufficient Kinesis shards to handle the rate of data flowing through the stream.

Which of the following is the BEST course of action that the developer should take to solve this issue and prevent this situation from re-occurring in the future?

An online magazine is deployed in AWS and uses an Application Load Balancer, an Auto Scaling group of EC2 instances, and an RDS MySQL Database. Some of the readers are complaining about the website’s sluggish performance when loading the articles. Upon checking, there is a high number of read operations in the database, which affects the website’s performance.

Which of the following actions should you take to resolve the issue with minimal code change?

A company has an AWS account with an ID of 061218980612 and has a centralized Java web application hosted in AWS Elastic Beanstalk that is used by different departments. The developer used the iam create-account-alias --account-alias finance-dept AWS CLI command to create a user-friendly identifier for the finance department.

For faster troubleshooting, the application must also be configured to easily trace all its downstream requests, such as Apache HTTP requests, AWS SDK requests, and SQL queries made using a JDBC driver. The ability to send traces to multiple different tracing backends without having to re-instrument the application code is required as well.

Which of the following options is the MOST suitable solution that the developer implements?

A developer has enabled API Caching on his application endpoints in Amazon API Gateway. For testing purposes, he wants to fetch the latest data, and not the cache data, whenever he sends a GET request with a Cache-Control: max-age=0 header to a specific resource.

Which of the following policies will allow him to invalidate the cache for requests?

The developer has built a real-time IoT device monitoring application that leverages Amazon Kinesis Data Stream to ingest data. The application uses several EC2 instances for processing. Recently, the developer has observed a steady increase in the rate of data flowing into the stream, indicating that the stream’s capacity must be scaled up to sustain optimal performance.

What should the developer do to increase the capacity of the stream?

An application experiences a sluggish response whenever there is a surge in requests involving read queries. The developer has already attempted to improve performance by optimizing the queries. However, the problem still persists even after applying the change. The application is hosted in an Amazon ECS Cluster and uses a MySQL database backed by Amazon RDS.

Which of the following could the developer do to resolve the performance issue? (Select TWO.)

A clickstream application uses Amazon Kinesis Data Stream for real-time processing. PutRecord API calls are being used by the producer to send data to the stream. However, there are cases where the producer intermittently restarted while doing the processing, which resulted in sending the same data twice to the stream. This inadvertently causes duplication of entries in the data stream, which affects the processing of the consumers.

Which of the following should you implement to resolve this issue?

The infrastructure of an application is designed such that a producer sends data to a consumer via HTTPS. The consumer may sometimes take a while to process the messages, which can result in unexpected timeouts and cause newer messages not to be acknowledged immediately. To resolve this issue, a developer decided to introduce an Amazon SQS standard queue into the system. However, duplicate messages are still not being handled properly.

What should the developer do to ensure that messages are durably delivered and to prevent duplicate messages? (Select TWO.)

A developer is managing a real-time fraud detection system that ingests a stream of data using Amazon Kinesis. The system works well with millisecond end-to-end latency, but the allocated shards are way underutilized based on the performance data in CloudWatch.

Which of the following is the MOST suitable solution to reduce the cost and capacity of the stream?

A developer has recently deployed an application, which is hosted in an Auto Scaling group of EC2 instances and processes data from an Amazon Kinesis Data Stream. Each of the EC2 instances has exactly one KCL worker processing one Kinesis data stream which has 10 shards. Due to performance issues, the systems operations team has resharded the data stream to increase the number of open shards to 20.

What is the maximum number of running EC2 instances that should ideally be kept to maintain application performance?