Since you got rid of the MySQL bottleneck, it seems your server architecture now simply isn't able to handle higher concurrency. If you suddenly got 5-10x the n

Since you got rid of the MySQL bottleneck, it seems your server architecture now simply isn't able to handle higher concurrency. If you suddenly got 5-10x the number of users, you'd have the same problems as before adding your AJAX queueing, right? That's, of course, assuming nothing else "breaks" first due to the increased traffic.