The Netflix team managed to squeeze out some huge performance improvements over Active Model Serializers:
We want to ensure that with every change on this library, serialization time is at least 25 times faster than Active Model Serializers on up to current benchmark of 1000 records.
At first glance I thought this was a drop-in replacement for AMS, which would've been epic, but it has its own API. That being said, its API is pretty similar and looks easy to use.
Exactly how much faster is this library? It can serialize 250 records in 3.01 ms vs AMS's 138.71 ms!