Which of the below mentioned solutions is cost effectiv…

A customer has a website which shows all the deals available across the market. The site
experiences a load of 5 large EC2 instances generally.
However, a week before Thanksgiving vacation they encounter a load of almost 20 large
instances. The load during that period varies over the day based on the office timings.
Which of the below mentioned solutions is cost effective as well as help the website achieve
better performance?

A.
Setup to run 10 instances during the pre-vacation period and only scale up during the office time
by launching 10 more instances using the AutoScaling schedule.

B.
Keep only 10 instances running and manually launch 10 instances every day during office hours.

C.
During the pre-vacation period setup 20 instances to run continuously.

D.
During the pre-vacation period setup a scenario where the organization has 15 instances running
and 5 instances to scale up and down using Auto Scaling based on the network I/O policy.

Explanation:
AWS provides an on demand, scalable infrastructure. AWS EC2 allows the user to launch OnDemand instances and the organization should create an AMI of the running instance. When the
organization is experiencing varying loads and the time of the load is not known but it is higher
than the routine traffic it is recommended that the organization launches a few instances before
hand and then setups AutoScaling with policies which scale up and down as per the EC2 metrics,
such as Network I/O or CPU utilization. If the organization keeps all 10 additional instances as a
part of the AutoScaling policy sometimes during a sudden higher load it may take time to launch
instances and may not give an optimal performance. This is the reason it is recommended that
the organization keeps an additional 5 instances running and the next 5 instances scheduled as
per the AutoScaling policy for cost effectiveness.
http://media.amazonwebservices.com/AWS_Web_Hosting_Best_Practices.pdf