Does 800+ seem  to be the threshold for the number of Avsim users online at one time before we start getting slow loads, System Unavailable errors, and blank screens?  Could this be caused by significant number of users keeping the site loaded when they are away from their computers?  All I know is when I see 800 or more users online I start to subconsciously hear that OOM bong we know from FSX.  (note: said subconsciously).  Its at that point also where I believe we start to see duplicate posts, as users may be getting a system unavailable page after attempting to post a message.   If I note 800+ and am posting I make it a habit to highlight, right click, and copy the text of my message to clipboard in case the post does not complete.

Probably also depends on what those 800+ people are doing.  A web server serving static content can really crank things out, when you add in features of database queries (lookups) and app server work, you start to bring down the environment throughput.  When I run web  stress test for work, when we get up in those big numbers, you start to stress different parts of the environment such as database or app server or even web server, then things start going down hill.  You have to identify what exactly is the problem such as an index that is missing or needs defragmenting or maybe you have logging turned up too high and the app server is just writing everything to log (and spending less time servicing requests) that the programmer does not need anymore for debugging or maybe you just need good old more horsepower: cpu, memory or faster drives.  You have to look at each piece and it sounds like they mentioned MySQL database is in question here.