Reserved Instances

aws/billing aws/cost-management

💡 Definition

Reserved Instances (RIs) provide a significant discount (up to 72%) compared to On-Demand pricing and provide a capacity reservation when used in a specific AZ.

🔑 Key Concepts

Commitment: 1-year or 3-year term.
Types:
- Standard RIs: Highest discount, least flexible (cannot change instance family).
- Convertible RIs: Lower discount, allows changing instance family/OS/tenancy.
Capacity Reservation: Can reserve capacity in a specific AZ.

⚙️ How it Works

Select Attributes: Instance Type, Region, Platform, Tenancy.
Choose Term: 1 or 3 years.
Choose Payment: All Upfront, Partial Upfront, No Upfront.
Billing Benefit: Automatically applied to matching running instances.

🎯 Use Cases

Steady-State Usage: Database servers or web servers that run 24/7.
Budget Predictability: Locking in a lower rate for long-term projects.

💰 Pricing Model

Discounted Hourly Rate: You pay for the hours in the term regardless of usage (unless you sell them on the RI Marketplace).

📝 Exam Tips (CLF-C02)

RIs are available for EC2, RDS, ElastiCache, OpenSearch, Redshift.
Standard vs Convertible: Standard has deeper discount; Convertible offers flexibility.
Regional vs Zonal: Regional RIs do not reserve capacity; Zonal RIs do.

See Also: * Savings Plans * EC2