I apologize in advance if this has been asked/answered a lot. I don't know enough yet to know what I don't know.
We have a Wordpress site on a typical LAMP shared hosting platform that was getting hundreds of hits per day. We're getting more popular and this number is now approaching 1000.
At times it is SLOW or simply times out. The site allows for image downloads and tracks those by user in a database so it's essentially a very primitive, unpaid "store." I mention that because it will probably get slightly more DB inserts than a typical very small Wordpress site.
My question is: what are the factors that will matter most in scaling this up? Ideally, we would not recode anything and the server would magically handle the traffic better.
To my mind, there are 3 issues:
The number of simultaneous visitors being served static pages
The static content of all the images people might view or download (20gb)
The mySQL databse processing each request via PHP.
I've seen various articles on dedicated servers, using several nameservers to load balance, managed hosts and cloud services.
As I wrote, I'd like some feedback as to how to measure what is causing the bottlenecks and then which types of services we should consider to make the greatest improvement with the least effort and cost for our scenario. IOW: how can I predict the impact of different upgrades we might attempt (VPS vs. cloud service vs. managed host, etc.)