1. A company runs an e-commerce website that uses Amazon DynamoDB where pricing for items is dynamically updated in real time. At any given time, multiple updates may occur simultaneously for pricing information on a particular product. This is causing the original editor's changes to be overwritten without a proper review process. Which DynamoDB write option should be selected to prevent this overwriting?

A) Batch writes
B) Concurrent writes
C) Conditional writes
D) Atomic writes



2. A Lambda function is packaged for deployment to multiple environments, including development, test, production, etc. Each environment has unique set of resources such as databases, etc. How can the Lambda function use the resources for the current environment?

A) Hardcore resources in the source code.
B) Use environment variables for the Lambda functions.
C) Use separate function for development and production.
D) Apply tags to the Lambda functions.



3. A Developer wants to use AWS X-Ray to trace a user request end-to-end throughput the software stack. The Developer made the necessary changes in the application tested it, and found that the application is able to send the traces to AWS X-Ray. However, when the application is deployed to an EC2 instance, the traces are not available. Which of the following could create this situation? (Select two.)

A) The instance role does not have 'xray:BatchGetTraces and 'xray:GetTraceGraph permissions.
B) The X-Ray daemon is not installed on the EC2 instance.
C) The X-Ray endpoint specified in the application configuration is incorrect.
D) The instance role does not have 'xray:PutTraceSegments and 'xray:PutTelemetryRecords permissions.
E) The traces are reaching X-Ray, but the Developer does not have access to view the records.


4. A Developer must re-implement the business logic for an order fulfilment system. The business logic has to make requests to multiple vendors to decide where to purchase an item. The whole process can take up to a week to complete. What is the MOST efficient and SIMPLEST way to implement a system that meets these requirements?

A) Create an AWS SQS for each vendor, poll the queue from a worker instance, and joint the results.
B) Use Amazon CloudWatch Events to orchestrate the Lambda functions.
C) Use AWS Step Functions to execute parallel Lambda functions, and join the results.
D) Use AWS Lambda to asynchronously call a Lambda function for each vendor, and join the results.



5. An application has hundreds of users. Each user may use multiple devices to access the application. The Developer wants to assign unique identifiers to these users regardless of the device they use. Which of the following methods should be used to obtain unique identifiers?

A) Use IAM-generated access key IDs for the users as the unique identifier, but do not store secret keys.
B) Assign IAM users and roles to the users. Use the unique IAM resource ID as the unique identifier.
C) Implement developer-authenticated identities by using Amazon Cognito, and get credentials for these identities.
D) Create a user table in Amazon DynamoDB as key-value pairs of users and their devices. Use these keys as unique identifiers.