BUG #16334: We recently upgraded PG version from 9.5 to 10.10 and system performance is not so good

The following bug has been logged on the website:

Bug reference:      16334
Logged by:          Tejaswini GC
Email address:      tejaswini.gc@decathlon.com
PostgreSQL version: 10.10
Operating system:   Centos 7
Description:

Hello Team,

We have upgraded our database into version 10.10.
After upgrading we could see that the system performance is bad , and one of
the applications linked to it via web service is not working.

During this upgrade we have not done any code changes either on the
application side or on our ERP side.

We are trying to debug everything from application perse, but till now we do
not have any lead.

Can you tell us are there any measures that we need to take after upgrade.

What is the ideal setup or paramters that we should have when we upgrade to
v 10.10

Thanks