[sethammons]

By default, yes, FKs and joins. However, I tend to work on high scale systems generally backed (primarily) by mysql. To scale out (tbs of data, hundreds of tables, millions of users, billions of daily interactions), we've had to remove some FKs, avoid db triggers, use caching heavily (including piggy backing requests where you don't serve an identical request from the db, you wait for the response and returned the memoized version). When you do choose to remove a FK, the need doesn't go away, you just move it. Now you have to look into data sync and out-of-band integrity checks and you have to have a plan on what to do when you go looking for data that is no longer there.