I'm sure there are ion bindings for every language in common use at Amazon. But a huge percentage of Amazon code is Java, so presumably this one was the best maintained and documented.
I doubt it, when I was there Ion was only used by only a handful of Java teams doing backend work. It was also horribly documented and supported at the time (3.5 years ago).
I am still in Amazon and Ion is definitely the most widely used library around. It has among the best documented code and some of the extensions that have been built on top of Ion are simply amazing.
