Exam AWS Certified Solutions Architect - Associate SAA-C03 topic 1 question 146 discussion

In the Question is mentioned that it has o Demand instances...so I think is more cheapest reserved and spot

Answer is B: Reserved is cheaper than on demand the company has. And it's meet the availabilty (HA) requirement as to spot instance that can be disrupted at any time. PRICING BELOW. On-Demand: 0% There’s no commitment from you. You pay the most with this option. Reserved : 40%-60%1-year or 3-year commitment from you. You save money from that commitment. Spot 50%-90% Ridiculously inexpensive because there’s no commitment from the AWS side.

B is the correct answer, using reserved instances is definitely more cost effective than using on-demand instances.

B for sure

Agree with others

This is a bit unclear, but B seems the best option of the ones given. Usage is either "heavy" (during the 8 hours), "moderate and steady" (overnight) or "low" (during weekends). So there is always SOME usage, which could be covered by a few Reserved Instances (which would be cheaper than On-Demand Instances). A - "Spot instances for the entire workload", might 'affect the availability of the application' B - Seems the best answer C - More expensive than B D - Dedicated instances aka dedicated hardware -> very expensive

I vote for C: Please explain me if I am wrong: If application experiences heavy usage during an 8-hour period each business day and all other time we don't need them? it mean than on-demand price will be only 33% from total cost so saving will be near 66%, more than reserved instances all other load we can cover by spot instances. So why it not C?

Selected Answer: C On-Demand Instances are more appropriate than Reserved Instances because "The application is used heavily for a period of 8 hours every weekday" requirements.

The answer should be C. Because if reserved is chosen, you have to pay for every hour. I calculate from this pages (if I'm wrong please correct me) https://aws.amazon.com/ec2/pricing/reserved-instances/pricing/#:~:text=Reserved%20Instances%20provide%20you%20with,instances%20when%20you%20need%20them. Example: for t4g.nano Reserved instances (0.003X24X365)+(1.90X12)=49.08 On demand instance (0.0042X8X365)=12.264 it will be added spot instances

B, since the application needs to be on 24/7 for business days; on weekends, it can be off at any moment. The question mentions something like 8 hour per business day but!!! this is just for heavy usage, the application is also on during overnight.

Why it's not A ? the application is "stateless" so it can be interrupted at any moment and the spot option is the cheaper one.

If we assume moderate usage of 8 hours on average every day a week, this should be on demand, since it is not a 24/7 server. There is downtime on the weekends and after the initial 8 hours.

Answer is C as the Jobs won't run for 24hrs/day hence Reserved instances is not required. As the Job runs for 8hrs/day we can choose On-Demand Instances

C is most cost effective option for running not 7x24 loads

I see some internet post about On-Demand vs Reserved below. I also think the argument from the (C) camp is valid. But (B) is not wrong. Just depends on usage. quoted from: https://www.pcapps.com/services/aws-reserved-vs-on-demand-instances/ If you know you are only going to use a particular server part-time – say, 8 hours a day, 5 days a week – we recommend purchasing On-Demand Instances for those servers. If you are unsure which instance type is most appropriate for your performance needs, our advice is to start with any On-Demand Instance for a month or two, and experiment with changing the Instance Type up or down to see it performs. The goal is to “dial into” the lowest cost instance type that meets your performance needs. We recommend that you purchase Reserved Instances only when you know you are going to use it close to 24×7 (or at least more than 75% of the time).

For 8 hours/day on demand works best

Main concern here is cost and availability. Reserved Instances provide you with significant savings on your Amazon EC2 costs compared to On-Demand Instance pricing. Spot instances et you take advantage of unused EC2 capacity in the AWS cloud. Spot Instances are available at up to a 90% discount compared to On-Demand prices. You can use Spot Instances for various stateless, fault-tolerant, or flexible applications.