web2py or grok (zope) on a big portal,
Zope and the ZODB have been used with big applications, but I'd still consider linking Zope with MySQL or something like that for serious large-scale applications.  Even though Zope has had a lot of development cycles, it is usually used with another database engine for good reason.  As far as I know, the argument applies doubly for web2py.
I am planning to make some big project (1 000 000 users, approximately 500 request pre second - in hot time).
For performance I'm going to use no relational dbms (each request could cost lot of instructions in relational dbms like mysql) - so i can't use DAL.
My question is:

how web2py is working with a big traffic, is it work concurrently? I'm consider to use web2py or Gork - Zope,
How is working zodb(Z Object Database) with a lot of data? Is there some comparison with object-relational postgresql?

Could you advice me please.