MemoryPack: Zero encoding extreme performance binary serializer for C# (github.com)

XTREEEEM

memcpy() was the best and fastest serializer from the start. It already existed in 1983.

Surprised how well the Orleans serializer performs for most uses cases.

It's nice when you're absolutely sure you won't need schema evolution. Then go for it. If you have a tiny bit of doubt, use a binary alternative that supports it, which for me is Protobuf. You'll get gRPC support for free, which you'll most likely need anyway.