[endymi0n]

I‘m smelling the SQL case could be reasonably easily thrown together with PostgreSQL and a custom Foreign Data Wrapper based on protobuf-c (prior art: cstore_fdw by the Citus folks). Proto definitions then should compile rather cleanly to table definitions, at least one level down (PG isn‘t so good with nested structures).

The main thing stopping this endeavour is probably that to the best of my knowledge, there isn‘t any standardization in the Protobuf community about file formats serializing multiple of these together like RecordIO - that, and my C skills are pretty rusty by now :)