> Zero-copy formats usually turn out to be worse for use as in-app data structures, because they have to carefully control memory allocation and layout in a way

> Zero-copy formats usually turn out to be worse for use as in-app data structures, because they have to carefully control memory allocation and layout in a way that makes it hard to mutate an already-constructed message. Oh, I never thought of it that way, but that makes perfect sense. I guess I just assumed messages would be collections of pointers and buffers living "somewhere" in memory, but of course the actual layout can make a ton of difference. I guess there is an implicit rule that if you are dealing with inbound structures in a read-only fashion, passing around the serial structure is OK for when the field access cost is minor compared to the copy cost, but if you want to mutate it, or doing lots of access operations where that isn't trivial, it makes sense to copy into your own data structure.