"5 times faster" reminds me of Cap'n Proto's claim: in benchmarks, Cap’n Proto is INFINITY TIMES faster than Protocol Buffers: https://capnproto.org/
I mean, cap'n'proto is written by the same person who created protobuf, so they are legit (and that somewhat jokish claim is simply that it requires no parsing).
In my experience capn proto is much less ergonomic.