Phase Verbs / Action Phrases
| Phrase | Meaning |
|---|---|
| reclaim (an instance) | AWS takes back a spot instance when spot price exceeds your max |
| cancel (a spot request) | stop AWS from launching new spot instances |
| terminate (an instance) | permanently stop and delete the instance |
| diversify (across pools) | spread instances across multiple launch pools for resilience |
| fulfill (a spot request) | AWS successfully launches the requested spot instances |
Technical Vocabulary
| Term | Definition |
|---|---|
| Spot Instance | EC2 spare capacity; up to 90% discount; can be terminated when spot price exceeds max price |
| Max Spot Price | User-defined ceiling price; instance runs while spot price ≤ max |
| Spot Price | Current market price for spare capacity in an AZ; fluctuates hourly |
| Two-minute grace period | Warning time before spot instance is stopped/terminated |
| Spot Request | A bid document defining instance count, max price, AMI, valid time range, and request type |
| One-time request | Spot request that disappears after instances are launched once |
| Persistent request | Spot request that automatically relaunches instances if they are interrupted |
| Spot Fleet | A collection of Spot Instances (and optionally On-demand) chosen from multiple launch pools |
| Launch pool | A combination of instance type, OS, and AZ available for Spot Fleet to draw from |
| lowestPrice strategy | Spot Fleet picks the pool with the cheapest price |
| diversified strategy | Spot Fleet distributes instances across all defined pools |
| capacityOptimized strategy | Spot Fleet picks the pool with the most available capacity |
| priceCapacityOptimized strategy | Spot Fleet picks highest capacity first, then lowest price within that (best for most workloads) |
Key Concepts
How Spot Pricing Works
- You define a max spot price you’re willing to pay
- As long as current spot price ≤ max price → instance runs
- If spot price exceeds max price → 2-minute grace period → instance stopped or terminated
- Spot price varies per AZ (same instance type can have different spot prices across AZs)
- Can be 60-90% cheaper than on-demand in practice
Spot Request Types
| Type | Behavior |
|---|---|
| One-time | Request fulfilled → instances launched → request disappears |
| Persistent | Request stays active; if instances are interrupted, AWS automatically relaunches them when price permits |
Correct Order to Terminate Spot Instances (Exam Critical!)
Wrong order (do NOT do this):
- Terminate instances first
- Spot request sees 0 instances → auto-launches new ones → you’re stuck in a loop
Correct order:
- Cancel the spot request first (prevents new instance launches)
- Then terminate the existing spot instances
A cancelled spot request does NOT automatically terminate already-running instances — you must do that yourself.
Spot Fleet
- A fleet = set of Spot Instances + optionally On-demand instances
- You define multiple launch pools (different instance types, OS, AZ combinations)
- Fleet automatically picks the best pool based on your chosen strategy
- Fleet stops launching when it reaches target capacity or budget
Spot Fleet Allocation Strategies
| Strategy | Behavior | Best For |
|---|---|---|
| lowestPrice | Always pick cheapest pool | Short workloads, max cost saving |
| diversified | Spread across all pools | Long workloads, high availability |
| capacityOptimized | Pick pool with most available capacity | When availability matters most |
| priceCapacityOptimized | Highest capacity first → lowest price within that | Best choice for most workloads |
Use Cases Summary
| Workload | Spot OK? |
|---|---|
| Batch jobs | ✅ Yes |
| Data analysis | ✅ Yes |
| Image processing | ✅ Yes |
| Resilient distributed workloads | ✅ Yes |
| Databases | ❌ No |
| Critical applications | ❌ No |
Exam Tips
- Spot = cheapest EC2, but interruptible — 2-minute warning before reclaim
- Persistent requests auto-relaunch → must cancel request BEFORE terminating instances
- One-time request: disappears after fulfillment — no auto-relaunch
- Spot Fleet picks from multiple pools; spot request targets one specific pool
priceCapacityOptimized= recommended strategy for most Spot Fleet workloadslowestPrice= best for short/quick cost-optimized tasksdiversified= best for long-running, high-availability workloads