At some point it's good to step back and examine each of these pieces and the resources they use. Even if you do, you may only tweak each component independent of the rest. Just like any large piece of software, every piece of a Web system affects every other. It would be good to step back and examine each piece in regard to the system as a whole. Examining what system resources each piece is using can prove very beneficial.
Most Web applications depend on a database back end.
A database is a common resource shared by different applications. An examination of database resource usage should answer a number of questions. The answer, probably, is too many. Just because a large system can support a huge amount of resource usage doesn't mean that having one will improve speed, reliability or scalability. This is exactly what we found while developing large Web systems for Oracle.