viewer is a Relay convention for wrapping fields in an authenticated context. If the viewer does not resolve (not logged in) then data.viewer is null. It makes

viewer is a Relay convention for wrapping fields in an authenticated context. If the viewer does not resolve (not logged in) then data.viewer is null. It makes view permissions checking a lot easier and simpler. Edges and node is also a Relay interface. Graphql can be simpler if you don't use relay. Also the relay client is quite fat. I use Apollo and I do use relay interface and conventions, just without the official Relay client. I like Apollo's simplicity a lot more.