journalctl output is overwhelming during an incident.
Narrow before you read: journalctl -u myservice --since "10 min ago" -p warning gives the unit, the window and the severity in one line. -o cat strips the metadata once you know where you are.
Two users need to write to the same folder without stepping on each other.
A shared group plus the setgid bit: chgrp team dir && chmod 2775 dir. New files inherit the group, which is the part plain chmod 775 misses and the reason it stops working on the second day.
Anything that changes this at ten times the scale?
At ten times the size the bottleneck moves from the operation itself to what it competes with: memory, locks and the people who have to run it. The approach stays, the batching gets smaller and the schedule matters more.