DAOS object has two-level keys: d-key and a-key (diagram on the left side), this is convenient for supporting complex data model. However, it is not always necessary because some scenarios only require one-level key, e.g. distributed KV store. Even in the current DFS implementation, the file object also has empty a-key just because DAOS object model has to have it.
In order to avoid the space/memory consumption of empty a-key, DAOS should define a new object type which is called flat-kv. With this object type, value can be directly attached to d-key (or just call it key), the entire a-key tree can be eliminated (diagram on the right side).
