You should describe more details of your application to get some reliable answers, imho... Is it CGI or pure mod_perl? Apache 1 or 2? How many rows exist in db tables and how complex queries are? How many requests per second? How much memory and CPU GHz? What is successive response time for you?
I can recommend to use some profiler to observe, what does the bottleneck really. Perhaps it is not SQL engine...

In reply to Re: OT: Scalable web application architecture by pajout
in thread OT: Scalable web application architecture by badaiaqrandista

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