1The Risk vs Reward of Spot
Spot instances offer the biggest savings but introduce engineering challenges. You cannot run a standard database on a Spot instance, as sudden termination would cause data corruption. However, for background workers, image processing, or containerized microservices behind a load balancer, Spot instances are the holy grail of cost reduction.
2The Flexibility of Savings Plans
Historically, companies bought Standard Reserved Instances, locking themselves into a specific instance family (e.g., m5). If they needed to upgrade to m6 a year later, the RI was useless. Compute Savings Plans solve this by applying the discount to ANY compute usage, making them the modern standard for baseline cost reduction.
3Step-by-Step Breakdown
The Cost of Compute. EC2 is often the largest line item on an AWS bill. Understanding pricing models is critical to running cost-effective cloud architectures.
On-Demand. On-Demand is the default. You pay for compute capacity by the second (for Linux) with no long-term commitments. It is the most expensive, but most flexible option.
Reserved Instances (RIs). Reserved Instances provide a significant discount (up to 72%) compared to On-Demand, in exchange for committing to a specific instance type and region for 1 or 3 years.
Savings Plans. Savings Plans are similar to RIs but offer more flexibility. Instead of committing to a specific instance type, you commit to a specific dollar amount per hour ($10/hr) for 1 or 3 years.
Spot Instances. Spot Instances let you bid on spare AWS capacity at steep discounts (up to 90%). However, AWS can reclaim the instance with only a 2-minute warning if they need the capacity back.
Pricing Check. Which pricing model is best for a stateless, fault-tolerant batch processing job that can be interrupted?
- →On-Demand
- →Reserved Instances
- →Spot Instances
Dedicated Hosts. Dedicated Hosts are physical servers fully dedicated for your use. They are the most expensive option, used primarily for regulatory compliance or specific software licensing (like BYOL).
Mixing Models. A mature architecture mixes models: RIs for the baseline database, On-Demand for baseline web traffic, and Spot instances for auto-scaling peaks.
Spot Fleet. A Spot Fleet automatically requests Spot instances from various capacity pools to maintain target capacity, handling interruptions gracefully.
Completion. You can now optimize your AWS bill.
