AWS Certified Solutions Architect AWS

QUESTION 251
You have a distributed application that periodically processes large volumes of data across multiple Amazon EC2 Instances. The application is designed to recover gracefully from Amazon EC2 instance failures. You are required to accomplish this task in the most cost-effective way. Which of the following will meet your requirements?
A. Spot Instances B. Reserved instances C. Dedicated instances D. On-Demand instances
Answer: A
Explanation:
Using reserved instances is not the most cost-effective way.
https://aws.amazon.com/blogs/aws/new-scheduled-reserved-instances/
“Scheduled Reserved Instance model allows you to reserve instances for predefined blocks of time on a recurring basis for a one-year term, with prices that are generally 5 to 10% lower than the equivalent On-Demand rates.”
You can get spot instances with much lower prices:
https://aws.amazon.com/ec2/spot/pricing/
“Spot instances are also available to run for a predefined duration – in hourly increments up to six hours in length – at a significant discount (30-45%) compared to On-Demand pricing plus an additional 5% during off-peak times for a total of up to 50% savings.”

QUESTION 252
Which of the following are true regarding AWS CloudTrail? Choose 3 answers.
A. CloudTrail is enabled globally. B. CloudTrail is enabled by default. C. CloudTrail is enabled on a per-region basis. D. CloudTrail is enabled on a per-service basis. E. Logs can be delivered to a single Amazon S3 bucket for aggregation. F. CloudTrail is enabled for all available services within a region. G. Logs can only be processed and delivered to the region in which they are generated.
Answer: ACE
Explanation:
A: have a trail with the Apply trail to all regions option enabled.
C: have multiple single region trails.
E: Log files from all the regions can be delivered to a single S3 bucket.
Global service events are always delivered to trails that have the Apply trail to all regions option enabled. Events are delivered from a single region to the bucket for the trail. This setting cannot be changed.
If you have a single region trail, you should enable the Include global services option.
If you have multiple single region trails, you should enable the Include global services option in only one of the trails.
D: Incorrect. Once enabled it is applicable for all the supported services, service can’t be selected.