I'm currently working on a social web application using python/django. Recently I heard about the PHP's weakness on large scale projects, and how hippo-php helped Facebook to overcome this barrier. Considering a python social web application with lot of utilization, could you please tell me if a similar custom tool could help this python application? In what way? I mean which portion (or layer) of application need to be written for example in c++? I know that it's a general question but someone with relevant experience I think that could help me.
Thank you in advance.
Don't try to scale too early! Of course you can try to be prepared but most times you can not really know where you need to scale and therefore spend a lot of time and money in wrong direction before you recognize it.
Start your webapp and see how it goes (agreeing with Spacedman here).
Though from my experience the language of your web app is less likely going to be the bottleneck. Most of the time it starts with the database. Many times it simply a wrong line of code (be it just a for loop) and many other times its something like forgetting to use sth. like memcached or task management. As said, find out where it is. In most cases its better to check something else before blaming the language speed for it (since its most likely not the problem!).
Python/Django - Web Application Performance