I'm not technically familiar with the computing and software infrastructure here but I would be very surprised if Mudcat is slowing down because the total number of posts is over 300,000. That is a rather paltry number of entries for database management systems to handle and I seriously doubt that it's having an impact.
A more signigicant measure of system load is the number of "hits" experienced by the system in a given period of time. It's the activity at the moment that, when heavy enough, can tax the system and slow it down. The fact that the forum archive has increased two hundred percent in the last year indicates that the Café is far more popular, worldwide, than in past years. Either that or there are a fair number of folks who have found some way to earn a living by sitting all day at their computers going post, post, post. (Please let me know how that works.)
At the end of the day, the solution to the problem is always the same... money. Money for infrastructure, money for software, money for development and system administration tasks. Sources of sustenance are all pretty well identified (well, Max hasn't started selling pop-up ads yet) so we need to ask ourselves if we are helping out as much as we can. Does everyone have at least one tee shirt? Do we always come to the Mudcat "Shameless Commerce" page first when contemplating a purchase? Do we send donations or offer items for auction? These are the behaviors that can result in faster service at the Café.
The U.S. Constitution guarantees the right of all citizens to freely express their opinions. Note, however, there is no provision to guarantee that opinions can be expressed for free.
I know this has all been said before but, as we all know, learning comes with repitition.