Match access to the data's purpose
Public access can make a file retrievable by anyone who knows or discovers its address, depending on the storage configuration. It is suitable for intentionally public assets, not as a shortcut for sharing confidential documents.
Private access requires a controlled delivery method, such as an authenticated application or a time-limited sharing mechanism supported by the service. Check who can issue access and whether links can be forwarded beyond the intended audience.
Review permissions as content changes
A file that was safe to publish can later be replaced with sensitive material under the same key. Tie access decisions to the content lifecycle and review policies when objects are overwritten, moved, or repurposed.
Test both allowed and denied cases without relying on a logged-in session that may hide exposure. Remove unnecessary public grants, confirm cached copies or shared links are handled according to the service's behavior, and document the intended audience.