Intraweb instantly 'crashes' when above 340 users

[Anto90]

We have an Intraweb 14.2.9 web application running for our customers, that that works smooth and very fast.

However, when we reach a critical amount of 340 sessions, the intraweb application instantly 'crashes' (response becomes too slow to even show the logon page). Logged on users can work for a little while, new users are directly unable to logon. There is no build up in slowness, it just instantly happens as soon as we reach the user amount.

This takes every time about 15 minutes to automatically resolve and returns back to normal, after which users can logon again and all is as fast as prior to the ordeal.
Due to less users, during weekends this never happens...on peak days it happens multiple times per day.

We did a lot of research on the complete infrastructure and architecture, and we tried several different solutions, but non seems to resolve the underlying issue.
We are now 100% sure that the issue is within the intraweb web application itself. We have multiple applications (mobile apps, web applications, windows applications) connected to the database, including an exact copy of the project with less users, and they all remain to work fine when this crash happens.

Last night we added 8 extra cpu's to the database server, just to see if we would go over the 340 sessions. It did not, it happens every time for 15 minutes.

Before we run into technical details, is this behavior something someone recognizes? Any clues on where to dig? We are running out of options, so any input would be welcome.

Thanks a lot!

Hi ,
In most cases is due to bad code. Thread safe not respecting memory leaks on code or access violation. Test with fastmm with fulldebug mode to test. 
I hope this can help