How Nginx Decides To Open Further PG Socket

[dinobagio]

Hi,
We've recently had an issue with NGINX (24 workers in our context) opening further connexions to postgre therefore leading to no more available slots for other services as DB was configured with a limited number of sockets (100 in our context).
I'm trying to understand how nginx decides to open new sockets to PG ?
Which criteria leads to opening a new socket ?
Thanks in advance for your help,