Hello,
I'm PostgreSQL expert for about 13 years. I have been working as a developer and DBA on large scale projects like Turkish e-government portal (over 20 million of users ) and Turkish Cable TV project (about 2 million users) many years. Both are PostgreSQL projects.
You should more explain to solve your problem. Do DBs have same data, DDL structure and infrastructure such as CPU, memory, disks (SSD, HDD, SAN etc.), operating system, file system etc.?