AWS Certified Solutions Architect EC2 Instance Types and Cost 3 — Questions and Answers
Question 1: A web application experiences predictable traffic spikes every weekday from 9 AM to 6 PM. Which Reserved Instance offering type provides the most savings for this scheduled pattern?
- Standard Reserved Instances with partial upfront
- Scheduled Reserved Instances (Correct answer)
- Convertible Reserved Instances
- Spot Instances with defined duration
Correct answer: Scheduled Reserved Instances
Scheduled Reserved Instances let you reserve capacity for specific time windows, matching predictable recurring workloads at lower cost.
Question 2: Which EC2 instance family uses AWS Graviton processors and is known for delivering the best price-performance ratio for general-purpose workloads?
- M5 instances
- M6g instances (Correct answer)
- C5 instances
- T3 instances
Correct answer: M6g instances
M6g instances use AWS Graviton2 ARM-based processors and offer up to 40% better price-performance than comparable x86 instances.
Question 3: A database server needs consistent, high CPU performance without throttling at any time. The workload runs at 70% CPU continuously. Which instance type is most appropriate?
- T3 burstable instance
- M5 general purpose instance (Correct answer)
- T3a with unlimited mode
- T2 standard instance
Correct answer: M5 general purpose instance
M5 instances provide consistent full-core CPU performance without bursting credits, suited for sustained high-CPU workloads.
Question 4: What is the primary difference between an EC2 Dedicated Host and a Dedicated Instance?
- Dedicated Hosts are cheaper than Dedicated Instances
- Dedicated Hosts give visibility and control over the physical server, Dedicated Instances do not (Correct answer)
- Dedicated Instances support BYOL licensing, Dedicated Hosts do not
- There is no practical difference between the two
Correct answer: Dedicated Hosts give visibility and control over the physical server, Dedicated Instances do not
Dedicated Hosts provide visibility into sockets and cores on the physical server (required for some BYOL licenses), while Dedicated Instances only guarantee hardware isolation.
Question 5: A solution architect needs to run a stateless web tier that scales from 2 to 50 instances based on load. Which purchasing strategy minimizes cost while ensuring baseline availability?
- 100% On-Demand Instances
- 100% Spot Instances
- Reserved Instances for baseline + Spot for scale-out (Correct answer)
- Dedicated Hosts for all instances
Correct answer: Reserved Instances for baseline + Spot for scale-out
Using Reserved Instances for the predictable minimum capacity and Spot Instances for burst scaling is the standard cost-optimized architecture.
Question 6: Which EC2 instance type is best suited for an in-memory database like Redis or Memcached at large scale?
- C5 compute-optimized
- R6g memory-optimized (Correct answer)
- I3 storage-optimized
- P3 GPU instance
Correct answer: R6g memory-optimized
R-family (memory-optimized) instances provide high RAM-to-CPU ratios ideal for in-memory databases and caching workloads.
Question 7: A company has unused Standard Reserved Instances it no longer needs. What should they do to recover value from these?
- Convert them to Spot Instances
- Sell them on the AWS Reserved Instance Marketplace (Correct answer)
- Transfer them to another AWS account for free
- Request a full refund from AWS
Correct answer: Sell them on the AWS Reserved Instance Marketplace
The AWS Reserved Instance Marketplace allows customers to sell their unused Standard RIs (not Convertible) to other AWS customers.
AWS Certified Solutions Architect EC2 Instance Types and Cost 3
A web application experiences predictable traffic spikes every weekday from 9 AM to 6 PM.
Which Reserved Instance offering type provides the most savings for this scheduled pattern?