For questions with a specific dependency on AWS ephemeral disks, which are available on some instances.
An ephemeral disk is an instance store which provides temporary block-level storage for your AWS instance. This storage is located on disks that are physically attached to the host computer. Instance store is ideal for temporary storage of information that changes frequently, such as buffers, caches, scratch data, and other temporary content, or for data that is replicated across a fleet of instances, such as a load-balanced pool of web servers.
Ephemeral disk is typically faster than EBS volumes.
The main downside of ephemeral disks is that they lose all data after a power off/on cycle of the instance. The data will probably survive a simple reboot, but that's not guaranteed.
AWS instances classes i2/3, c5d, d2, f1, g2, h1, m1/2/3, m5d, z1d, x1 and x1e have one or more ephemeral disks available to them, in addition to EBS volumes you may choose to attach. A full list may be found at https://ec2instances.info/?min_storage=1
