Ok I understand the intent better now. I don't like the idea of automatic "shortening" the names we need, that introduces several opportunities for bugs and quite some trouble with schema evolution over time.

+1 to allow the user explicitly customize the user name, -1 to try such an optimisation behind user's back.. we'd only save a handful of bytes.

Both Infinispan and JGroups use "type names" and "cluster names" which have to repeatedly be sent over the network to tag each and every UDP packet; the idea of setting up an initial hand-shake to agree on an encoding and then switch to transmitting a single byte (or just a couple) is a recurrent topic when it comes to performance optimisation, but there are just too many complexities not making it worth it, not least to make it a nightmare to identify when such a complexity is biting (vs something else going wrong).
There's a similar issue with "table name" strings in OGM's keys.

We can discuss this at the next meeting if someone things it can be done safely in the case of Search, but trust me that it's complex so I'm not sure if attempting that is worth our time.