Prepare previews for the visible photos in a selected album, then a small nearby window, so likely next clicks can show an image sooner.
Fetch visible and nearby iCloud photos in the background while giving the clicked photo priority.
Show a correct cached thumbnail or small local image while a larger preview loads, and cancel work as you switch albums or scroll away.
Album warmup stays bounded within the Photos image cache. iCloud transfer time still depends on Photos and the network. Browsing does not change your originals. Read the Photos guide.
Ingest