If Iris does propose to create keys following a sequence, how can we obtain a sequential number in another context?

In my case, I automatically create care centers, and I want to set them a number like:

APP-DD-999

APP = Name of the application used by the center
DD = center department number
999: sequential number in the department
It is of course possible that centers will be created in competition, so this possible competition must be managed.

5 3
0 232