Before we can even begin to decide on a processor count, we need a baseline. With a working PostgreSQL server to base our numbers on, we can just use the amount of existing users during a busy period. Without that, we need to guess. This guess can actually be pretty close, depending on how the application was targeted. If the intent is to service 1000 users per second, we should start there since that's the same assumption the company is using to buy application and web servers.
After that, we are applying a commonly accepted formula used by PostgreSQL administrators for a very long time. The ideal number of active connections is equal to twice the amount of available processor cores, plus the amount of disk spindles. Amusingly, ...
