How many concurrent visitors can pc handle?

Hi JWL, I assume you mean an SQL database as MySQL is not supported.
I haven't got any actual figures, but I am aware of  large stores with fairly high levels of transactions.
 

Hi JWL, that is actually a complex question. In short, there is virtually no limit.  However, it truly depends on the server's configuration (hardware, memory, etc.) and the amount of time you are willing to wait for a page to load.  For example, a shared web server that allocates a very small amount of memory to each domain will support less concurrent sessions than a dedicated server with unlimited memory consumption.   A better question is this:  How much memory does ProductCart use when there are “n” active customers?  Then you will have an idea about what your server can handle.  I will encourage some other active stores to help answer this question.  What I can tell you now is what Hamish said.  There are many ProductCart stores on properly configured servers handling tons of traffic.