Complete Guide to EC2 Reserved Instances
Save up to 75% on EC2 costs with Reserved Instances. Learn when and how to purchase RIs for maximum savings.
Introduction¶
Reserved Instances (RIs) are one of the most effective ways to reduce EC2 costs, offering savings of up to 75% compared to On-Demand pricing.
What are Reserved Instances?¶
Reserved Instances provide a significant discount (up to 75%) compared to On-Demand instance pricing. RIs are not physical instances, but rather a billing discount applied to running On-Demand instances in your account.
Types of Reserved Instances¶
Standard Reserved Instances¶
- Up to 75% off On-Demand prices
- Best for steady-state usage
- Can modify instance size within the same family
Convertible Reserved Instances¶
- Up to 54% off On-Demand prices
- Can change instance family, OS, and tenancy
- More flexibility for changing workloads
Payment Options¶
| Payment Option | Discount | Use Case |
|---|---|---|
| All Upfront | Highest discount | Maximum savings, have budget |
| Partial Upfront | Balanced | Good savings with some flexibility |
| No Upfront | Lowest discount | Cash flow friendly |
Best Practices¶
Pro Tip
Start with Convertible RIs if you're unsure about future requirements. The flexibility is worth the slightly lower discount.
1. Analyze Your Usage¶
Before purchasing RIs, analyze your usage patterns:
# Use AWS Cost Explorer or CLI to analyze usage
aws ce get-usage-and-costs --time-period Start=2024-01-01,End=2024-12-31
2. Right-Size First¶
Ensure your instances are properly sized before committing to RIs.
3. Consider Regional vs AZ-Specific¶
- Regional RIs: More flexible, apply to any AZ in region
- AZ-Specific RIs: Capacity reservation, higher discount
Conclusion¶
Reserved Instances are essential for cost optimization. Start conservative and increase RI coverage as you understand your usage patterns better.