What does website scalability consist of?

What do people consider scala开发者_JAVA百科bility? I've always hear people talk about writing scalable apps. But as a developer, I've never really saw any pointers/tips in an article that normal developers dont know. Such as caching db calls, etc. Mostly what I see are options that are configured by system admins or anyone dealing directly with the servers.

So my question is, from a developers perspective, do we really have much effect on a website's scalability? If so, could we be pointed towards articles that aids us on the .net framework. (ASP.NET MVC)

Also, do we have to write our apps differently if we were to accommodate adding new hardware, such as another webserver. (or is it the same app, but more instance of it?)

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You can maybe gather some input from here on SO:

What does scalability mean to you?

Engineering scalability into an application

Design Patterns (or techniques) for Scalability