[he0001]

> The minute you start two db transactions within one script you have eventual consistency.

Well it's all about errors (and subsequently about control and correctness). Even if you have two transactions you are able to undo the other without anyone else (readers of the system) know that it was there because something else happened just before yours. A transaction usually happens in an atomic fashion, which makes it possible to back out on something which is no more correct so you have to fail it somehow to someone which does have the ability to recover, the one who initiated the call.

Without being too philosophical, most, if not everything depends on synchronous state (fex events themselves), computing just gives the illusion of that things happens immediately. Eventual consistency is cheating, and you can do it where the events are entirely independent. Otherwise you will have side effects when events are not ordered.

JavaScript have an "asynchronous" coding style, where (red/blue) methods are put on event-loop as "events". But the events needs to executed in order (synchronously by a thread) for the program to behave correctly so you give the methods attributes (red/blue) for them to execute in an linked order. So even the asynchronous behaviour in JS relies on synchronous features for it to be correct!