I realise I made a mistake and hadn't actually used connect_configuration !

I think the issue is the bandwidth yeah, for example when I doubled the number of CPUs (which doubles the allowed egress) the time taken to upload halved. It is puzzling because as you say it's not that much to upload.

For now I've whittled down the number of entries to a more select but useful few and that has solved the issue. If it crops up again I will try connect_configuration properly.

Thanks for your help!