Just a guess here: I would have an agreed-upon key name suffix like "__b64_enc" or something. Serializers take a field "foo" of type bytes and serialize it as

Just a guess here: I would have an agreed-upon key name suffix like "__b64_enc" or something. Serializers take a field "foo" of type bytes and serialize it as "foo__b64_enc": b64(value), and deserializers strip and base64-decode. edit: it's exactly what you would do if you wanted to pass any binary data as json over the wire, regardless of whether you're using protobufs. you'd just get it "for free" (meaning you wouldn't have to write the boilerplate, not that you don't have to en/decode).