We noticed PHP-FPM failed in our setup due to ypbind not being ready at
the time PHP started. As PHP-FPM is all about running PHP instances as
isolated users, it is important that all user accounts are available
when it starts up. To ensure this is the case, we recommend the addition
of the following line to the [Unit] section of source file
debian/php-fpm.service

After=nss-user-lookup.target

We first discovered this in php7.4-fpm and had success by adding the
line via systemctl edit. It would be nice if this incorporates into the
debian package. The target nss-user-lookup should be good for any
generic user account system.

Regards,
Daohai