Check range support end to end
Send a test request with a byte range and verify the response status, Content-Range, and returned length. Some proxies may ignore or transform range headers, so validate the actual path users take rather than only querying the storage origin.
For resumable downloads, persist the object version or validator such as an ETag and confirm it has not changed before appending a later range. Otherwise chunks from different versions can be combined into a corrupt file.
Apply access and cache rules consistently
Ensure authorization applies to every partial request just as it does to a full download. Review whether signed links remain valid for the transfer duration and whether caches honor the intended access boundaries.
Test invalid and unsatisfiable ranges, interruption, and resume behavior with representative clients. Monitor response sizes and errors so an unsupported range request does not silently trigger a full-object download.