Profile vs iRule, case sensitivity, persistence

You could combine the two rules into one. Using HTTP::path will be more efficient than using HTTP::uri (which is the path and the query string).

 
 when HTTP_REQUEST { 
    if { [HTTP::cookie exists "SSO"] } { 
       pool SSO_Pool 
    } elseif {[string tolower [HTTP::path]] starts_with "/abcd" } { 
       persist cookie insert SSO 
       pool SSO_Pool 
    } 
 } 
 

That said, I'm not sure I understand your scenario completely. It sounds like you've had to use a single pool member at a time in order to get this to work. Could you instead have all four members set to the same priority and persist based on the four letter string in the URI along with UIE persistence? If you think this is possible, could you post a few anonymized examples of the requested URIs for two or three clients as they access the application?

Aaron