Hi,
hanks for comments.
Nothing is wrong with Apache, really nothing.
But if you use PHP and Apache, you can't store session data in the memory between two requests. You have to store the data in a data base, or use PHP sessions.

Let me describe it in a concrete case.

Suppose you have a community, using PHP, Apache and a data base MySql Sqlite, Oracle etc.

1. You use PHP sessions, to store the session data. Its fast and it is simple.

After a few months, you have have lots of visitors, and you have to scale. You buy a new server, and build a server farm. Now you have a problem, because the data you stored in PHP sessions on server one, is not available on server two.

Now you store the session data in the data base. On server tow, you have to connect on each request to server one, in order to fetch the data from the data base. Now you have connection overhead and your application becomes slow.

But that is not all, you get more visitors, and you have to buy a new server (server three). Now you have a real problem. Your data base cannot server so many queries.

It becomes seriose, when you begin to replicate your data base.

So nothing is wrong with apache, but some thing is wrong with PHP and Apache on huge sites.