I thought it was normal to do connection pooling as well, but I was pretty shocked when I saw how much the API at my job was murdering our PostgreSQL server. Every request meant a completely new connection. So while reads and writes were taking up maybe 10% of the server at peak times, creating and closing connections was taking up easily 5x more than that. If I was particularly unlucky, the PostgreSQL server would stall for a few minutes.

Still, I had to implement pgpool-II and do connection pooling that way. It was also a PHP application. :(