"A final alternative would be to use another storage engine, such as Badger or BoltDB (if we wanted to stick with Go). This alternative was not seriously considered for several reasons. These storage engines do not provide all the features we require, so we would have needed to make significant enhancements to them.
...
Lastly, various RocksDB-isms have slipped into the CockroachDB code base, such as the use of the sstable format for sending snapshots of data between nodes. Removing these RocksDB-isms, or providing adapters, would either be a large engineering effort, or impose unacceptable performance overhead.
"
"A final alternative would be to use another storage engine, such as Badger or BoltDB (if we wanted to stick with Go). This alternative was not seriously considered for several reasons. These storage engines do not provide all the features we require, so we would have needed to make significant enhancements to them. ... Lastly, various RocksDB-isms have slipped into the CockroachDB code base, such as the use of the sstable format for sending snapshots of data between nodes. Removing these RocksDB-isms, or providing adapters, would either be a large engineering effort, or impose unacceptable performance overhead. "
https://www.cockroachlabs.com/blog/pebble-rocksdb-kv-store/