Amazon Web Services Updated SAA-C03 Exam Questions and Answers by ralphie

 it allows the EC2 instances to read and write rapidly and concurrently to shared storage across two Availability Zones. Amazon EFS provides a scalable, elastic, and highly available file system that can be mounted from multiple EC2 instances. Amazon EFS supports high levels of throughput and IOPS, and consistent low latencies. Amazon EFS also supports NFSv4 lock upgrading and downgrading, which enables high levels of concurrency. References:

Amazon EFS Features

Using Amazon EFS with Amazon EC2

https://awscli.amazonaws.com/v2/documentation/api/latest/reference/ds/index.html

https://aws.amazon.com/premiumsupport/knowledge-center/dynamodb-high-latency/

Amazon DynamoDB Accelerator (DAX) is a fully managed in-memory cache for DynamoDB that improves the performance of DynamoDB tables by up to 10 times and provides microsecond level of response time at any scale. It is compatible with DynamoDB API operations and requires minimal code changes to use1. By configuring DAX for the new messages table, the solution can reduce the latency for reading new messages with minimal application changes.

B. Add DynamoDB read repticas to handle the increased read load. Update the application to point to the read endpoint for the read replicas. This solution will not work, as DynamoDB does not support read replicas as a feature. Read replicas are available for Amazon RDS, not for DynamoDB2.

C. Double the number of read capacity units for the new messages table in DynamoDB. Continue to use the existing DynamoDB endpoint. This solution will not meet the requirement of reading new messages with as little latency as possible, as increasing the read capacity units will only increase the throughput of DynamoDB, not the performance or latency3.

D. Add an Amazon ElastiCache for Redis cache to the application stack. Update the application to point to the Redis cache endpoint instead of DynamoDB. This solution will not meet the requirement of minimal application changes, as adding ElastiCache for Redis will require significant code changes to implement caching logic, such as querying cache first, updating cache after writing to DynamoDB, and invalidating cache when needed.

Reference URL: https://aws.amazon.com/dynamodb/dax/

User-defined tags are key-value pairs that can be applied to AWS resources to categorize and track them. User-defined tags can also be used to allocate costs and create detailed billing reports in the AWS Billing console. To use user-defined tags for cost allocation, the tags must be activated from the Organizations management account, which is the root account that has full control over all the member accounts in the organization. Once activated, the user-defined tags will appear as columns in the cost allocation report, and can be used to filter and group costs by product line. This solution will meet the requirements with the least operational overhead, as it leverages the existing tagging strategy and does not require any code development or manual intervention.

References:

1 explains how to use user-defined tags for cost allocation.

2 describes how to access and manage member accounts from the Organizations management account.

3 discusses how to create and view cost allocation reports in the AWS Billing console.