Biggest one I'm aware of is connections aren't threaded. And Pg tries to preallocate resources at the time of the connection. Together these make connections ex

Biggest one I'm aware of is connections aren't threaded. And Pg tries to preallocate resources at the time of the connection. Together these make connections expensive compared to Mysql's threaded connections. Many folks run a connection pooler in front of Pg for this reason. One pro of non-threaded is simplicity and no need for thread safety everywhere.