Information below is gathered from discussion with a zabbix user.
When we delete an item from template, linked to 10K hosts, it takes too much time, and in 99% of attempts it returms nothing (supposedly PHP error happens).
There were changes in
ZBX-6118, where it's stated:
Improved performance of create(), update() and template linkage methods for item, discoveryrule and itemprototype classes.
which does not include items deletion.
And one more thing:
We have a user with limited rights, access to only one host group with ~500 hosts. When opening Configuration -> Hosts, page is loading very long time.
A super admin user opens the same page really fast.
Note - I'm not sure what the provided debug belongs too - opening a page or deletion items.
Strange thing that debug section does not contain some fields if compare with a testing zabbix installation.