That is really a 'how long is a stick' question - it depends on what you're doing. If you're having trouble with performance, it might be that you can simplify your database structure or put in some optimisations (for example, saving some common data between relationships on write, rather than pulling the data on read).

If you want an 'out of the box' (sort of) performance module, have a look at the 'static publisher' module. It allows you to rsync the generated pages to your internet-facing site.

Usual rule of thumb is: "Avoid premature optimization". Once everything is working as it should, then you can use the profiler to see if there are some 'quick wins' to be made by combining queries or whatever.