A reader writes:" Persistence for object-oriented systems is an incredibly cumbersome task to deal with when building many kinds of applications: mapping objects to tables, XML, flat files or use some other non-OO way to represent data destroys encapsulation completely, and is generally slow, both at development and at runtime. The Object Prevalence concept, developed by the Prevayler team, and implemented in Java, C#, Smalltalk, Python, Perl, PHP, Ruby and Delphi, can be a great a solution to this mess. The concept is pretty simple: keep all the objects in RAM and serialize the commands that change those objects, optionally saving the whole system to disk every now and then (late at night, for example). This architecture results in query speeds that many people won't believe until they see for themselves: some benchmarks point out that it's 9000 times faster than a fully-cached-in-RAM Oracle database, for example. Good thing is: they can see it for themselves. Here's an article about it, in case you want to learn more."