When you first start using PostgreSQL you use it with the default parameters and you are confident that they have been chosen to provide a conservative but stable experience. As your knowledge of the database expands, you start reading the documentation more and more and then the time comes to tweak the parameters by yourself. The documentation clearly states that some parameters are more dangerous than others, eg. fsync = off, but there are plenty more parameters that, in the right circumstances, can cause the database to misbehave, to become very slow, or to just stop working and fail. This presentation will present a handful of parameters and theoretical (or better yet absurd) situations in which the specific values chosen can cause problems. Some of the problems are interesting, some annoying and some are just unbelievable. If time allows, the most interesting situations will be demonstrated on a running instance of PostgreSQL.