> A good example would be going from "direct DB access" to "global memcache" to "local memcache backed by global memcache" - all without application changes. I

> A good example would be going from "direct DB access" to "global memcache" to "local memcache backed by global memcache" - all without application changes. I strongly disagree: I'd rather debug something wrong with the lone application level change which added the cache support at the application level, rather than have to enter the long and deep rabbit hole of the path the code takes at the point I ask for a resultset and I get something from the DB-backed ORM, or from a global memcache, or blah. But then again, I happily develop on mostly-Perl codebase(s) ;)