A company runs a production application on a fleet of Amazon EC2 instances. The application reads the data from an Amazon SQS queue and processes the messages in parallel. The message volume is unpredictable and often has intermittent traffic. This application should continually process messages without any downtime.
Which solution meets these requirements MOST cost-effectively?
To meet the requirement of continuous processing without any downtime, it is crucial to have a reliable and available baseline capacity. Reserved Instances (RIs) provide a cost-effective solution for this baseline due to their lower cost compared to On-Demand instances. For handling unpredictable and intermittent traffic, On-Demand Instances are the best fit because they offer the flexibility to scale up quickly and do not risk interruption like Spot Instances. Therefore, the combination of Reserved Instances for the baseline capacity and On-Demand Instances for additional capacity ensures both reliability and cost-effectiveness.
"without any downtime" - Reserved Instances for the baseline capacity "MOST cost-effectively" - Spot Instances to handle additional capacity
Dude, read the question, cost consideration was not mentioned in the question.
Dude, read the question, "Which solution meets these requirements MOST cost-effectively?"
I am leaning towards C because the idea of having a queue is to decouple the processing. If an instance goes down(spot) while processing will it not show up back after the visibility timeout? So using spot meets the cost-effective objective.
Intermediate data stored in SQS queue so once free then it take data and process.
cost-effectively means, Cheapest solution (cost) that achieve all the requirements (effectively). Its not cost-effectively if is just cheapest solution that fail to address all the requirements, in this case. (This application should continually process messages without any downtime) no matter the volume, since it is unpredictable. B for example, address the requirement but not the cheapest solution that achieve it. D is the cheaper choice that address the requirement (without any downtime). and C is cheaper than D but do not garantee that you wont have downtime since it is SPOT instances.
How can you have baseline capacity when your message volume is unpredictable and often has intermittent traffic?
For this reason I think correct answer is A
Spot instances cannot be an option as it is unreliable and the question requires the messages to be continuously processed
D is the correct answer
C is correct, read for cost effectiveness
if you cannot find enough spot instance you will have downtime you cannot always find spot instance
Why downtime when there are baseline reserved instances?
When traffic spikes and there happens to an increase in the spot price, if the price exceeds the threshold set then there would be downtime as no additional compute can be acquired. Hence even if spot instances are more cost effective, I would interpret the cost effective requirement to be the ability to reliably acquire new instances and dispose of when not needed, hence on demand instances
AWS has stopped issuing spot instances so i think C
so i think C is incorrect*. the Correct ans is D.
I think this phrase "This application should continually process messages without any downtime." killed the idea of using Spot instances, not 100% sure though.
Reserved Instances for Baseline + On-Demand for unpredictable volume and intermittent traffic without downtime. Keywords: 1. Production Application 2. Unpredictable Volume and intermittent traffic 3. Without any down-time Spot-instances is a cheaper option, but cannot guarantee downtime, and it is subject to availability too, hence the best choice is to go for On-Demand instances.
reserved for baseline + on-demand for additional C will work but spot does not guarantee "continually process messages without any downtime" spot instance may not even be available so what happens with the messages which exceed baseline requirements?
Dude without downtime - spot instances might interrupt the processing if it goes away. So correct answer is D
C for sure
Reserved Instances (RIs) provide a cost-effective way to cover the baseline capacity, ensuring a predictable number of instances are always available. Spot Instances can handle additional capacity during traffic spikes, providing scalability without committing to a specific number of instances. This combination (C) offers the most cost-effective solution, as RIs cover the baseline and Spot Instances handle variable demand. Why not D? On demand is expensive than Spot instances.
If it is a spot instance, it may become unusable. Since the question states that there is no downtime, I think D is more in line with the purpose.
key word - production System & without any down time. This excludes spot instance.
C is correct because MOST cost-effective reason
Using Reserved Instances (RIs) for baseline capacity ensures a lower cost for the instances that are constantly required to maintain the application's baseline workload. RIs offer significant cost savings compared to On-Demand instances, making them a cost-effective choice for steady-state workloads. Spot Instances can then be utilized to handle additional capacity during periods of higher message volume. Spot Instances provide spare EC2 capacity at significantly reduced prices compared to On-Demand instances, allowing for cost savings during peak workloads. Since the message volume is unpredictable and often intermittent, Spot Instances can efficiently handle the fluctuating demand without incurring high costs.
Missing some information to make a proper decision. What does "without downtime" mean? We are already outside of Realtime processing, and messages can remain in the queue until picked up. Purely using Spot instances _might_ do just fine, but there could be times when no spare capacity is available. How much delay is acceptable? I'd go with reserved+spot, but reserved+on demand may be required for priority on bursty load. B is the one option i would rule out completely. The workload is unpredictable, we can't reserve infinity instances for all eternity.
Keywords are - Production, without any downtime. I would prefer D option as AWS itself recommends, spot instances should not be used in Prod environment.
Answer is C Reserved Instances for the baseline capacity can be used to handle downtime issue and Spot Instances to handle additional capacity is the most cost effective
Cheaper option which meets requirement
C is correct. Because - This application should continually process messages without any downtime -> RI for baseline workload - The message volume is unpredictable and often has intermittent traffic. -> Spot instances or on demand instances - Which solution meets these requirements MOST cost-effectively -> Spot instances (ruling out/dismissing on demand instances