Note that the underlying data store where a lot of the byte churning happens is RocksDB, written in C++. Also the Go/C++ interface in CockroachDB is coarse to reduce overheads.
For some reason(s) nobody is using LMDB on distributed dbs (only know actordb). While for single-nodes there are many cases that have switched and been better.
Like even TiDB (mysql protocol, golang) uses TiKB (kv in rust,rocksdb) to make it faster.