This is one of the most common questions we see and is unfortunately impossible to answer accurately. The resources required to run a given site will depend on a number of factors:

• How optimized is the code being run
• What optimization steps have been taken in the stack serving this app
• How are your users interacting with the site (A visitor to youtube who is streaming video uses a lot more server side resources than one browsing wikipedia and reading text).

In general with 14k concurrent users I would recommend scaling horizontally, running one database server (to start) and multiple web nodes serving your app. There are other architectural decisions to make around implementing this type of change but in the long run it will be easier to scale.

The best way to determine the resources you would need is to do some load testing on your own. Figure out what resources 1 or 10 users require and scale that estimate up.