Does Django Scale? - Stack Overflow
The cache system is awesome. But you need to have a strong database design.
Alot of the time it takes a interesting tricks with the cache to get a ton of performance but that is the case no matter what lang/framework you use.
Another note is that parts of the washingtonpost run django. The top answer has links to 2 really good articles, you can also search youtube for django con scale and see a talk from the curses.com guy.
