It is my understanding that AppSync doesn't really support offline first yet. I would encourage you to keep an eye on efforts by the community such as Apollo repo you linked or the Khan Academy project mentioned in it.

If you need something _now_ you are probably better of looking outisde the GraphQL ecosystem though.

You should also consider what your need is. If you need true offline support (ie, you have an app that needs to fully function for days without internet) then that is a very different scenario from just needing to have a bit of data cached for the duration of a subway ride.