How to get private files from cloud storage with file permission check (S3, Spaces etc.)?

Question

API

Good time!
There is a site that uploads files to the Spaces (DigitalOcean) cloud storage, taking advantage of cloud storage in their delivery of files to the client depending on the location. But it's so good if the files are public.
Problem:
What about private files, access to which can only be obtained after verification in the application (only authenticated user, verification of access rights to this file, and so on)?
Solution:
Add a route to the application to receive such private files from the cloud storage with access control. But in this case, all the advantage of storing files in the cloud is lost and this route in the application (proxy) becomes a bottleneck in this approach.
Question:
Maybe there are other approaches to solve this problem so that there is no such bottleneck?
I would be very grateful to hear your approaches!