EC2 Savings Plans vs Reserved Instances: Which to Choose?
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?
⚠ Common exam trap
Test-takers frequently confuse Compute Savings Plans with Reserved Instances, assuming that any long-term discount requires locking into a specific instance family, but Compute Savings Plans provide both the discount and the flexibility to change instance families, which is the key differentiator tested in this question.
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
✓
Compute Savings Plan
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.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
S3 Intelligent-Tiering
Why it's wrong here
S3 Intelligent-Tiering is a storage class for objects, not a compute purchase, so it cannot discount EC2 usage. It is tempting because it also reduces cost for predictable access patterns, but the requirement is an EC2 commitment retaining instance-family flexibility, which a Compute Savings Plan provides.
- ✗
Dedicated Instances
Why it's wrong here
Dedicated Instances give physical host isolation, not a usage discount, so they fail the cost-saving requirement. They tempt teams needing hardware-level tenancy or licensing compliance, where a single-tenant host is mandated. Here, a Compute Savings Plan or Convertible Reserved Instance delivers the discount with instance-family flexibility.
- ✓
Compute Savings Plan
Why this is correct
A Compute Savings Plan commits to a fixed hourly spend for one or three years, applying discounted rates across EC2 instance families, sizes, and Regions, delivering the required discount while preserving the instance-family flexibility the team needs.
- ✗
Spot Instances only
Why it's wrong here
Spot Instances are spare capacity that AWS can reclaim with two minutes' notice, so they cannot sustain a continuously running three-year archive. They tempt teams chasing the deepest discounts for interruption-tolerant batch work. A Compute Savings Plan or Convertible Reserved Instance provides the discount while permitting instance-family changes.
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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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.