EC2 Savings Plans vs Reserved Instances: Which to Choose?
A line-of-business application runs on EC2 instances 24/7 with predictable usage for the next year. The application will stay in the same Region, and the team does not want to manage capacity interruptions. Which two purchase options can reduce cost compared with pure On-Demand pricing? Select two.
Quick Answer
The answer is Standard Reserved Instances and Compute Savings Plans. Both reduce costs versus On-Demand by requiring a 1- or 3-year commitment for predictable, steady-state workloads, with Reserved Instances offering up to 72% off for a specific instance family in a region and Compute Savings Plans providing up to 66% off with flexible coverage across instance families, regions, and even Fargate or Lambda. On the SAA-C03 exam, this scenario tests your ability to distinguish between commitment-based discounts that guarantee no capacity interruptions—a common trap is choosing Convertible Reserved Instances or Spot Instances, which either lack interruption protection or require instance flexibility trade-offs. Remember the key distinction: if the workload is steady and you want the highest discount with capacity assurance, pick Standard Reserved Instances; if you need flexibility across compute services, pick Compute Savings Plans. A useful mnemonic is “Steady and Standard, Flexible and Savings.”
⚠ Common exam trap
Many exam-takers think Spot Instances are always cheaper and safe for steady workloads, but they forget the interruption risk, or they may confuse Dedicated Hosts with Reserved Instances as a cost-saving measure, when Dedicated Hosts actually increase cost for physical isolation.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Buy Compute Savings Plans for the expected steady usage.
Compute Savings Plans (A) offer a flexible discount (up to 66%) in exchange for a 1- or 3-year commitment to a consistent amount of compute usage (measured in $/hour), automatically applying to any EC2 instance family, region, or even AWS Fargate/Lambda. This reduces cost compared to On-Demand while avoiding capacity interruptions, as the commitment covers the predictable steady-state usage. Standard Reserved Instances (B) provide a similar discount (up to 72%) for a specific instance family in a specific region, also with a 1- or 3-year term, and guarantee capacity for the specified AZ if you choose a zonal reservation, ensuring no interruptions.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Buy Compute Savings Plans for the expected steady usage.
Why this is correct
Compute Savings Plans reduce the hourly cost of predictable usage while preserving flexibility across supported compute services. They are a strong fit when the workload is steady and the team wants savings without interruption risk.
- ✓
Purchase Standard Reserved Instances for the EC2 fleet.
Why this is correct
Standard Reserved Instances are designed for steady EC2 usage in a specific Region and can significantly lower the effective hourly rate versus On-Demand. They align well with a one-year predictable workload that must remain continuously available.
- ✗
Move the fleet to Spot Instances.
Why it's wrong here
Spot Instances can be much cheaper, but they may be interrupted when spare capacity is reclaimed. That directly conflicts with the requirement to avoid capacity interruptions for a continuously running application.
When this WOULD be correct
A question where the application is fault-tolerant, stateless, or can handle interruptions gracefully (e.g., batch processing, big data, or containerized workloads) and cost reduction is the primary goal without strict uptime requirements.
- ✗
Use Dedicated Hosts to reserve physical servers for the application.
Why it's wrong here
Dedicated Hosts are typically chosen for licensing or isolation requirements, not for the lowest general-purpose compute price. They usually cost more than commitment-based pricing options for a normal steady-state workload.
When this WOULD be correct
A question requiring a license that is tied to a specific physical server (e.g., Windows Server with per-socket licensing, or Oracle Database with per-core licensing) and where you must ensure compliance by not sharing the server with other customers. In that scenario, Dedicated Hosts would be the correct choice despite higher cost.
- ✗
Stay entirely on On-Demand Instances because they are already the cheapest option.
Why it's wrong here
On-Demand provides the highest flexibility, but it is not the lowest-cost model for predictable 24/7 usage. The scenario explicitly calls for reducing cost, which requires a commitment-based discount.
When this WOULD be correct
If the question asked 'Which option provides the most flexibility with no upfront commitment and no capacity interruptions?' then staying on On-Demand would be correct because it offers maximum flexibility and no interruption risk.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The SAA-C03 exam frequently reuses these exact scenarios with slightly different constraints.
✓Buy Compute Savings Plans for the expected steady usage.Correct answer▾
Why this is correct
Compute Savings Plans reduce the hourly cost of predictable usage while preserving flexibility across supported compute services. They are a strong fit when the workload is steady and the team wants savings without interruption risk.
✗Move the fleet to Spot Instances.Wrong answer — click to see why▾
Why this is wrong here
Spot Instances can be interrupted with a 2-minute notice, which violates the requirement to 'not manage capacity interruptions' for a 24/7 predictable workload.
★ When this WOULD be the correct answer
A question where the application is fault-tolerant, stateless, or can handle interruptions gracefully (e.g., batch processing, big data, or containerized workloads) and cost reduction is the primary goal without strict uptime requirements.
Why candidates choose this
Candidates know Spot Instances offer significant cost savings (up to 90% off On-Demand) and may overlook the interruption risk, especially if they focus only on cost reduction without reading the 'no capacity interruptions' constraint.
✗Use Dedicated Hosts to reserve physical servers for the application.Wrong answer — click to see why▾
Why this is wrong here
Dedicated Hosts provide physical servers dedicated for your use, but they are significantly more expensive than On-Demand instances and do not offer cost savings over Reserved Instances or Savings Plans for predictable workloads.
★ When this WOULD be the correct answer
A question requiring a license that is tied to a specific physical server (e.g., Windows Server with per-socket licensing, or Oracle Database with per-core licensing) and where you must ensure compliance by not sharing the server with other customers. In that scenario, Dedicated Hosts would be the correct choice despite higher cost.
Why candidates choose this
Candidates may think that reserving physical servers (Dedicated Hosts) is similar to Reserved Instances and would reduce costs, but Dedicated Hosts are actually a premium offering for licensing compliance, not a cost-saving measure.
✗Stay entirely on On-Demand Instances because they are already the cheapest option.Wrong answer — click to see why▾
Why this is wrong here
On-Demand Instances are the most expensive option; the question explicitly asks for purchase options that reduce cost compared to pure On-Demand pricing, so staying entirely on On-Demand does not reduce cost.
★ When this WOULD be the correct answer
If the question asked 'Which option provides the most flexibility with no upfront commitment and no capacity interruptions?' then staying on On-Demand would be correct because it offers maximum flexibility and no interruption risk.
Why candidates choose this
Candidates may think On-Demand is already cost-effective or that other options introduce complexity, but they overlook that Reserved Instances or Savings Plans offer significant discounts for steady-state workloads.
Analysis generated from the official SAA-C03blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Quick reference
Cloud Service Model Comparison
| Model | You Manage | Provider Manages | Examples |
|---|---|---|---|
| IaaS | OS, runtime, apps, data | Hardware, hypervisor, networking | EC2, Azure VMs, GCP Compute Engine |
| PaaS | Apps and data | OS, runtime, middleware, hardware | Elastic Beanstalk, Azure App Service |
| SaaS | Data and settings only | Everything else | Microsoft 365, Salesforce, Workday |
| FaaS / Serverless | Function code only | Infra, scaling, runtime | Lambda, Azure Functions, Cloud Run |
| CaaS | Containers and apps | Kubernetes, OS, hardware | EKS, AKS, GKE |
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About these practice questions
This SAA-C03 question is part of Courseiva's 302-question bank — original exam-style content with full explanations and wrong-answer analysis, never real exam questions or exam dumps. Learn why practice questions differ from exam dumps →
Same concept, more angles
1 more way this is tested on SAA-C03
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A production log archive runs continuously on EC2 with predictable usage for the next three years. The team wants a discount while retaining some instance-family flexibility. What should they buy?
medium- A.S3 Intelligent-Tiering
- B.Dedicated Instances
- ✓ C.Compute Savings Plan
- D.Spot Instances only
Why C: The Compute Savings Plan (C) is correct because it offers a discount (up to 66%) in exchange for a commitment to a consistent amount of compute usage (measured in $/hour) for a 1- or 3-year term, while allowing flexibility to change instance families, sizes, OS, tenancy, and even regions within EC2, Fargate, and Lambda. This matches the requirement of predictable usage for three years with instance-family flexibility, unlike Reserved Instances which lock to a specific instance family.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This SAA-C03 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the SAA-C03 exam.