Q:

after_create called after failed saved?

I want to send request to external software whenever I am certain that a model is saved. 
1) How do I determine the order in which after_create is called?
2) does it get called on a failed create? 
The RAILS API documentation says:

Note that this callback is still wrapped in the transaction around save.

3) Does this mean it requires the save to be successful before after_save is called or does it mean that once save is called after_save is always triggered? 

A:

How would I learn in what order after_create is called and if it
  persists through a failed create?

You can read the order of callbacks here:
http://api.rubyonrails.org/classes/ActiveRecord/Callbacks.html
If the transaction fails, the save event (and create/update events) return false. This will stop all later callbacks from being run. So, after_save, after_create/after_update all never get run on a failed save (or on a failed create/update).
...and the transaction gets rolled back so the database is not actually updated.

