This library is very helpful in the classic 1+n scenario, where the n queries are caused by following relationships.

There is another, less common scenario, with similar consequences: The original query defers some field, and then the field is accessed when going over the objects. It may seem very unlikely, because deferring has to be done explicitly, but can still happen when the deferring and the access are done in different parts of the code, and much like the classic case, can be improved by adding a call (e.g. defer(None)).