Here are some sad news for you: The flexibility of JSON and CBOR cannot be matched by any schema based system, because it is equivalent to giving up that advantage.

Sure, the removal of a field can cause an application level error, but that is probably the most benign form of failure there is. What's worse is when no error occurs and the data is simply reinterpreted to fit the schema. Then your database will slowly fill up with corrupted garbage data and you'll have to restore from a backup.

What you have essentially accomplished in your response is to miss the entire point.

There are also other problems with protobuf in the sense that the savings aren't actually as big as you'd expect. E.g. there is still costly parsing, the data transmitted over the wire isn't significantly smaller unless you have data that is a poor fit for JSON.

It's also worth noting CDDL [1], which adds schema-like utility to CBOR (and technically JSON.) We've started to use it in more places where we use CBOR.

[1] https://datatracker.ietf.org/doc/rfc8610/