Check identity and integrity
Keep the object key and upload result associated with the user's operation so a retry cannot accidentally point to another file. Compare the stored size with the expected length and use a checksum calculated from the content when the provider exposes compatible checksum support.
Do not treat an ETag as a universal content hash; its meaning can differ for multipart uploads and across providers. Use the storage service's documented checksum fields or download and verify content when stronger assurance is required.
Confirm access and readiness
For private objects, test retrieval through the authorized application path rather than making the object public just to verify it. Check content type and metadata if downstream processing depends on them.
Mark the file ready only after the checks your product requires have passed. If verification fails, keep the object quarantined or retry safely, report a useful error, and clean up abandoned temporary uploads according to policy.