While website loading speed testing I found that website is sometimes loading very quickly and some times it takes lot of time to start loading. When I checked it in detail, I found on some requests wait time was just in few hundred milliseconds, while on some other request which was slow it was actually taking 5 to 30 seconds in wait time.
What may be the cause of this kind of deviation from few milliseconds to 30 or more seconds. And how to improve it.
The site is build upon ASP.net MVC3 and Microsoft SQL Server database.
What patterns are there i.e. are the same URLs always slow, and other URLs always fast, or does it just appear to be random?
Look at what else is running on the server, is it a dedicated server or a VPS?
Look at the DB performance i.e. is it consistent, which are the queries that are taking the longest time, most CPU, most IO etc.
How busy is the site, do the slowdowns match when the app-pool is being recycled or started up?