A little bit of overkill recommendations here. With 10 users you don't "need" to separate out the database layer. Heck you don't need to do that with 100 users

A little bit of overkill recommendations here. With 10 users you don't "need" to separate out the database layer. Heck you don't need to do that with 100 users. Website I ran back in 2007-2010 had tens of thousands of users on a single machine running app, database, and caching fine. Users are actually a really poor way use for scalability planning. What's more relevant is queries/data transmission per interval, and also the distribution of the type of data transfers. I'd say replace the "Users" in this posts to "queries per second" and then I think it's a better general guide.