[skydhash]

> Why is everyone trying to check for things they don't have to?

I forgot where I read it (maybe something about testing or DDD), but an idea I like much is to not validate stuff coming from an external system other than for your internal constraints. You don't control an email account and how it was created and the specification is messy, so if you want to check for its existence, you query the other system. Same for other identifiers.