Spot Instances
- What it is
- Buy unused EC2 capacity at up to 90% off On-Demand.
- AWS can reclaim the instance with a 2-minute warning when it needs the capacity back.
- When to use
- Fault-tolerant, stateless, interruption-tolerant work.
- Batch jobs, CI/CD build fleets, big data analysis, image/video rendering, non-critical test environments.
- When not to use
- Databases, stateful single-node applications, anything that cannot resume.
- Not to be confused with
- On-Demand Instances — never interrupted, but full price.
- Reserved Instances / Savings Plans — discount for commitment, not for accepting interruption.
- Exam signal
- “Cheapest option” + “can tolerate interruption” → Spot. If interruption is unacceptable, Spot is always the wrong answer.