[SloopJon]

Do I understand correctly that the record layer is only usable by Java clients? That strikes me as a drawback of the layer approach: unless you supply a server protocol, like the document layer does, every language essentially reimplements the layer from scratch. That seems to be the case for the tuple layer, for example.

[gregwebs]

It certainly doesn't have to be the case. The MongoDB layer can be used via the MongoDB protocol. TiDB is an entire MySQL implementation that any MySQL client can connect to which is built on top of TiKV (equivalent to FDB). If the goal is lower overhead of data transfer, another approach is writing layers in C (or Rust exposed as C) and then generating bindings for different languages.