Thanks for your reply.
Rendering two (non nested) properties seems to not to impact performance.
Ive read at Ember is very slow at rendering lists about the {{group}} helper before, but wrapping {{#each}} with it in my application, causes an error (“TypeError: Cannot read property ‘view’ of undefined”).
I tried using {{#each groupedRows=true}}, and unbound too, but neither could help that much.
Seems like the cause lies in computed properties that Ember Data generates for related models.
Render time does not exceed 10ms if i use a custom property that returns a random model from the store instead of DS.belongsTo (for author in the example).
Models are always pushed to store to discard computed properties cached values.
I do this intentionally to simulate my application where i noticed browser lag when changing page number.
When models are downloaded from server, they are pushed to store by the adapter, and even if these were in the store previously (and not need to be instantiated), the push & render secuence impacts performance heavily when using relations.