Same here, I wrote an exchange core that did this using SBE. Basically you don't serialize in the classical sense, because you're simply taking whatever bytes are at your pointer and using them as some natural type. The internals of the exchange also simply used the same layout, so there was minimal copying and interpreting. On the way out it was the same, all you had to do was mask a few fields that you didn't want everyone to see and ship it onto the network.

Even an unoptimized version of this managed to get throughput in the 300K/s range.

Somehow it's the endpoint of my journey into serialization. Basically, avoid it if you need to be super fast. For most things though, it's useful to have something that you can read by eye, so if you're not in that HFT bracket it might be nicer to just use JSON or whatever.