Regarding the "configure your web site’s Auto scaling group to use spot instances rather than on demand instances" answer, I can put a spot price the same as a on-demand price in the "Maximum price" field of the Launch Configuration. Doing so I will keep the spot instances running.
Regarding the "consolidate many smaller RDS instances into a single larger RDS instance" answer we learnd that it’s sometimes cheaper to have a large instance type instead of many smaller types. Despite the savings are not sure, this is a valid option.
I am also concerned about such things in the exam. The answer is theoretically correct, but others have another opinion on that. Would it be a fail on such questions?
Yes, some things items like these in the real world can fall down on on either side, but on the exam there will always be at least one piece of information that makes a single answer correct. For example, I recently put an analytics solution in place for a customer and during the proof of concept phase we were trying to determine what instance size would be ideal for the customer. We ran several of their largest queries a discovered that using a much larger sized instance ran the queries so much faster than a medium sized instance that they actually saved money by going larger. On the exam, there will be some information like average query execution time or the like that will drive you toward a correct architecture and sizing to ensure its not a matter of opinion.
This challenge is a bit ambigouos. I think having reserved instances is a cost savings strategy. Also the questions is asking for which of the answers are "reasonable" reasonable is a relative term.
The spot price can go above the ON-Demand price which would terminate your instance causing no durability. Another way you could always make sure to keep your Spot Instances is setting it to a super high number like 100$ in theory never loosing them, but then what happens when the spot price rises above the on-demand instance? You know are loosing out on the cost saving part of the question. I agree with the RDS statement, but keep in mind on the exam it will tell you to "Pick the 2 best" or whatever. Thus assuming that you would save money is not a good thing to think. His questions are open for inturpretation on how many answers are correct which is actually good practice. The only 2 answers that would always save you money and keep durability are the ones he gave use.
You now* sorry for the typo