Simple definition
S3-compatible storage exposes objects through APIs modeled on Amazon S3, although feature compatibility varies by provider.
Purpose and use
S3-compatible storage exposes all or part of an API modeled on Amazon Simple Storage Service for objects and metadata.
How does it work?
Clients use an endpoint, credentials and operations supported by the provider.
Example and verification
Test required operations, including multipart upload, reading, deletion and any protection features used by the application.
Points to watch
Compatible does not mean identical: versioning, locking, consistency and limits can vary by service.
In short
Validate compatibility against application features and recovery scenarios.