Stig 8-34 seconds per one image update does not look good. As I understand, program is currently writing down faces into metadata, so it is quite natural that there are delays. There are good reasons this feature is off by default. But 20 seconds per image - that seems a lot. Probably your NAS is indeed very slow.
Stig Like if there was possible to make “liste over pending changes” and have them written later.
Tonfotos already is very asynchronous, lots of operations are queued, not exectued immediately. Almost all of them.