The Pizza compiler has a rather long startup time before it can begin to compile source files: since the compiler itself is written in Pizza, several class files must be loaded. PizzaExpress is a compiler that doesn't exit after compilation, so that class files don't have to be reloaded for the run of the compiler.

After starting PizzaExpress, source files entered at the prompt are compiled. Moreover, PizzaExpress associates a number with each of the filenames it compiles during one session, so recompilation of a file requires only entering that number. Filenames entered as command-line parameters to PizzaExpress will be assigned such numbers immediately.

PizzaExpress is distributed as part of the pizza.compiler package (version 38 and above) as both source code and class files to provide an example of invoking the Pizza compiler from within Java/Pizza code.