ephemeral
- What it means
- Short-lived: the resource’s data exists only as long as its host does, and disappears when that host stops or is replaced. The opposite of persistent.
- Where it shows up in AWS
- EC2 Instance store — the canonical example. Data survives a reboot, dies on stop, hibernate, or terminate.
- AWS Lambda
/tmp— scratch space for the life of the execution environment. - Container filesystems, and any instance in an Amazon EC2 Auto Scaling group that can be replaced at any moment.
- Why the design matters
- Treating servers as ephemeral (cattle, not pets) is what makes auto scaling, self-healing, and immutable deployments possible.
- The corollary: state must live somewhere durable — Amazon S3, Amazon Elastic Block Store (EBS), Amazon Elastic File System (EFS), or a database — not on the instance.
- Exam signal
- “Temporary”, “scratch”, “cache”, “buffer”, “data lost when the instance stops” → ephemeral storage.