The most recent release of Xodus states:
This release offers Service Provider Interface for I/O customization in the package jetbrains.exodus.io. In addition to default disk-based I/O, it lets you configure your application to use an in-memory database, or to access in read-only mode disk-based database opened in another JVM. You can also create your own I/O provider, e.g., for storing data in a remote/cloud file system.
Does it mean the S3 is ready or ready to be plugged into Xodus through the SPI?
In version 1.3.0, storing data in any remote/cloud file system is not supported out of the box.