The commonly accepted formula for estimating max_connections is to take the number of processor cores, multiply them by two, and add disk spindles. With the relatively recent improvement of virtual cores, contributing factors such as SSD or other high-performance storage, and so on, we have a bit more freedom than we had earlier. In addition, even if we were to follow this estimation method, allowing a few extra connections can prevent highly visible connection rejections. A slightly lower performance is a small price to pay for availability.
The advice for shared_buffers is very different from the accepted practice of simply setting it to a quarter of the available RAM. We must consider buffer flushing and the synchronization ...
