flatbuffers is great, as are binary blobs that are directly accessible without deserialization (such as my pocket-db) or rust `speedy` (barely any deserialization really, but it does still copy).  It is funny how copying something actually makes a performance difference for us. That is how fast we are now. For most people a memory copy (with its concomitant malloc) is trivial and lost in the noise of their real performance bottlenecks.