what points should I consider for very very high traffic website
I am creating the social networking site in PHP framework. I am thinking about points. 

Server technology
Database and Indexing
Caching (memory and database and file)
Load balancing

Can somebody help me with points. What all points I should think.
what points should I consider for very very high traffic website
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I am creating the social networking site in PHP framework. I am thinking about points. 

Server technology
Database and Indexing
Caching (memory and database and file)
Load balancing

Can somebody help me with points. What all points I should think.