When developing an application is it standard to architect the caching strategy concurrently or after the app is built?

Caching a complex application can get hairy very quickly. My question is do developers 开发者_开发百科generally build their caching strategy in WHILE developing the application or is it easier to build the application and then go back and layer a caching strategy on top of it?

One thing I find myself doing (when building caching in at the same time I develop an application) is constantly refactoring pieces of the application which affects the caching mechanisms I've just implemented for those parts of the application. Then I have to refactor both the application AND caching mechanisms.

I don't know if there are specific reasons for or against either strategy. If it's completely subjective then I apologize!

I'd have thought that any sensible separation of concerns in a design/implementation should allow for the addition of caching at a later date.

That said, for an application that's likely to require caching in the short to medium term, it would seem wise to implement the necessary caching interfaces/classes, etc. even if they're simply returning un-cached data in the initial implementation.