An interesting comparison might be to something like sending protocol buffers over the wire instead of JSON [1]. You can make a 100% valid and spirited defense

An interesting comparison might be to something like sending protocol buffers over the wire instead of JSON [1]. You can make a 100% valid and spirited defense of JSON (human readable! lots of open source tooling!) which at Facebook's scale is trumped by "well it works 20% faster and we have 400 million users that will see the benefit". And that scale aspect of this really matters. OP is completely correct in the criticisms that X_NEW_THING can be done in REST, but with the number of users + infrastructure that Facebook is dealing with, small improvements can really matter. 1 - https://code.facebook.com/posts/872547912839369/improving-facebook-s-performance-on-android-with-flatbuffers/ https://code.facebook.com/posts/872547912839369/improving-fa...